CA1168663A - In-board weighing apparatus - Google Patents

Abstract

Abstract of the Disclosure An inboard weighing apparatus for a load carrying machine such as a truck comprising small size, low mass strain gauges welded directly to the suspension of the machine. The gauges are located at areas of the suspension to give prime indications of strain. There is provided an electronic circuit to translate the measured strain into an electronic signal and a visual device for displaying the electronic signal as units of weight.

Description

t)~3 IN-BoARD WEIGHING APPAR~TUS
This invention xelates to Ineans for weighing the load on a load-carrying machine such as a truck, whereby a read-out of the weight is provided ~o the driver within the cab of the vehicle.
It is important for the driver of a load-carrying vehicle such as a transport truck to know the weight of a load which is being carried. Most roads have weight limits, and it is normal practice for such vehicles to be weighed at various off-highway locations to check on the gross weight ~o of the vehicle. Should the weight exceed a given maximum, fines are imposed. As it is unfeasible for scales to be installed at each loading location, judgment must be made as to the degree of load carried by the vehicle, and often the transport of a load becomes expensive due to the fines which are incurred due to excess loadin~.
It is therefore desirable that an in-board display be provided in the cab of the vehicle to show the driver the load weight which is being carried, from the moment of loading. Excess loads can therefore be removed prior to transport.
Prior to this invention, there were a number of known methods for determining bo~h gross and tare weight of a vehicle~ As already noted, a basic method comprised a fixed platform scale, which, while fairly accurate is highly in-convenient because of its infrequency of availability and because of the difficulty of unloading owing to the unusual distance of the scale from the loading site.
Another type of device and method utilized an on-boara deflection measuring device which included a load cell ~o placed between the truck chassis and the load being carried.
While more convenient than the earlier noted platform scale, load cells have several inherent problems r For instance, the .) 3 load cell must be of sufficient size and strength to support the load. The vehicle must undergo struc~ural alterations which can adversely affect the designed strength of the truck, its height and weight, etc. ~lso, load cells do not measure the true weight of the vehicle in that no provision is made for measuring changes in the ~are weight of the vehicle.
Other devices have used a form of strain sensing transducer attached to equalizing beams on a vehicle suspension to measure strain in the suspension as changes in weight~
~0 However, such devices have not proved satisfac~ory in that the strain sensing transducers are of large size and, because of their size, cannot be located at prime signal areas in the vehicle suspension. Further, the strain sensing trans ducers cannot be welded to the vehicle suspension but rather must be bolted or other~ise secured thereto and, as a result, considerable difficulty in mounting the transducers is experienced.
In addition, because of a physical separation of the strain sensing gauges in the transducer and the vehicle sus-pension to which the transducer is attached, there is a problem of temperature differential between the gauges and suspension which results in inaccuracies in the read out of the gauges.
Further, the points on ~he vehicle suspension for a~tachment of the transducers are areas of high vibration and it is virtually impossible to secuxe the transducers to the vehicle suspension without problems of loose contact between the transducers and the suspension.
Finally ,here is a type o~ on-board weighing system utilizing an arm which moves with movement of the load-carry-3~ ing box of the truck, relative to the truck chassis, but do,es not support the weight of ~he load. In this system, however,

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~ there are disadvantages in that again the tare weight of thetruck is not measured, and there is difficulty in calibration in that since a mechanical system is used, the amount of deflection is partly based on the degree of stress previously placed on the springs suppor~ing the box. Should there have been creep due to excess previous deformation, the rate of deflection per unit weight will not conform with that of the springs when originally installed. Furthermore, exposure of the linkage mechanism to the elements can eventually result o in inaccurate measurements and miscalibration of this type of system. Furthermore, a standard set of linkages and in-board scales would be unfeasible for a large variety of vehicles (or even for the same kind of vehicle), due to different spring constants, levels of the vehicle load box, and the like, for different vehicles.
The present invention measures both gross and tare weights of a vehicle and displays the weight in the cab sf the vehicle. The sensors employed in this invention are of small size and low mass and are welded directly to the vehicle suspension to become an integral part of the suspension and thereby minimi e temperature exror in the sensor read-ou~. In addition, the sensors, being of small size, may be located at the prime signal areas of the vehicle suspension and may be welded thereto by conventional welding techniques and welding skills. The welding of the sensor to the vehicle suspension eliminates error problems resulting from a loosenin~ of attach-ment of the sensor to the vehicle suspension and rPsults in a device which may be easily secured to a desired vehicle, quickly and easily calibrated by controls within the vehicle cab and separately calibrated for each vehicle. The calibration can be easily checked and, should recalibration be required, it is a simple ~rocess to do so,

- 3 -within the cab. External components need not be adjusted.
In addition, the sensors in this invention may be applied not only to equalizing beams but also to other major types of suspension used on trailers as for example "REKO"
four spring air bag suspensions or single axle vehicles.
In the present system, the 'oad of a trailer can be displayed in the cab of the pulling vehicle, and indeed, the total of the trai}er and main vehicle weights can be displayed.
These a~vantages are obtained in accordance with one aspect of the invention, by the provision of an in-board weighing apparatus in a machine for supporting a load comprising. means for carrying a load, at least one ~ase support member containing a path through which th~ major weight of the load supported thereby principally acts, a strain gauge fixed at a point along Ithe path to a surface of the base support memb~r for detecting the maximum strain caused by load on the support member, an electronic circuit connected to the strain gauge for translating the degree of strain detected into an electronic signal, and means connected to the circuit to display the degree of strain, calibratea in units a~ of weight, to display the weight of the load carr~ed by the machine.

The invention, in another aspect, resides in an in-board weighing apparatus for use in a load-carrying vehicle, comprising:
(a) means for detecting the variation in resistance of a stxain gauge, (b) a bridge circuit having said means for detecting as a variable element, including a bridge balance control, for providing a strain output signal, (c) a source of reference potential, (d) first means for selecting alternatively the strain output signal or the reference potential, * Trademark i 3 (e) a signal output display for indicating the strain in units of weight, and (f~ an output level control connected between said means for selecting and the signal output display for setting the output display to zero when the reference potential has been selected by the selecting means.
Where the load carrying machine is a vehicle, it i5 important the strain gauges be a~tached at prime signal areas of the vehicle suspension. Prime signal areas according to this invention are areas on the vehicle suspension which may be under compression or tension only from the vehicle load and are not areas that come under compressive strain when the vehicle is braked. In prior art devices located on equalizing or walking beams between vehicle axles, it has been found that braking of the vehicle places the equalizing beam under compression and the braking stress is then shown as weight to¦

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give a false reading. The present device rigidly secured to the vehicle suspension in a prime signal area away from areas acted on by braking stress will provide accurate indication of the load weight on the ~ehicle.

A better understanding of the invention will be obtained by reference to the detailed description below, in conjunction with the following drawings, in which:
Figure 1 is a schematic plan view of a steering axle, associated wheels and frame of a vehicle such as a transport truck, Figure 2 is the schematic view of a pair of drive axles, associated wheels and frame of the truck, Figure 3 is a plan schematic view of a pair of axles, associated wheels and frame of a trailer, Figure 4 is a schematic side elevation of a bogey such as might be used in conjunction with a railway flat car, Figure 5 is a schematic side elevation of a four spring suspension system commonly used in trailer suspensions;
Figure 6 is a schematic side elevation of an air-bag suspension system;
Figure 7 is a schematic side elevation of a single axle vehicle suspension; and Figure 8 is a partly schematic and partly block diagram of an electronic circuit for providing the output display.
Turning first to F gure 1, a steering axle 1 of a vehic]e cab is shown, at the ends of which are loca-ted wheels 2 and 3, a well known construction. Frame 4 is attached to the axle 4 in a well known manner, as by intervening springs, etc. The load carried by the truck is partly supported by the axle 1 via such springs and frame 4.

~ 3 A strain gauge S is bonded to the upper surface of the axle 1 and centered be~ween the whe~l5 2 and 3. Alter-natively, it could be bonded to the under surfaceO It has been found that these locations are the prime signal areas for the present i~vention, that is, centered between the vehicle wheels, To apply the strain gauge, it is preferred that the axle be bufed to provide a smooth clean surface~ The strain gauge is then spot welded to the axle, and a metal impàct shield spot welded over the strain gauge. The cavity between the strain gauge, axle, and shield should then be filled with liquid rubber such as SILASTIC** RTV, to avoid corrosive action of the environment, such as~salt water, etc. The AILTEK WELDABLE STRAIN GAUGE model SG129-5S has been found to be particularly suitable, and the spot welder an AILTEK W1200 WELDERn An electrical cable from the strain gauge should then be brought into the cab of the vehicle with suitable strain relief, and with provision for flexing due to variation ~o in distances between the axle and cab due to compression of the vehicle springs.
Turning now to Figure 2, the drive axles 6 and 7 of the cab are shown, held together by walking beams 8. The drive axles 6 and 7 have eight wheels 9 located at the ends of the drive axles, and distributed as shown. Of course, there may be only a single drive axle, rather than the two shown.
It has been found that maximum stress caused by weight is on the beams 8 at a point immedlately above or below the center bearing~ A strain gauge 10 welded to the upper center surface of one of the beams 8 and a strain gauge 11 welded to the bottom center surface of the other beam 8 will now respond to the maximum weight and at the same time produce a self-cancelling of errors caused by any temperature change * `
Trade M,~lk - 6 -** Trade Mark , 8 ~ ~) s~

and by compressive stress of turning or braking~ The st,rain gauges 10 and 11 are bonded to the frames 8 in a manner similar to that of the steering axles as described previously.

Figure 3 shows a pair of coupled axles 12 and 13 of a trailer to be pulled by the vehicle. The axles are coupled by means of frame 14. Eight wheels 15 are located at the ends of axles 12 and 13 in a well known manner.
For this structure a pair of strain gauges 16 and 16a are fixed to the frames 14 similarly to the gauges 10 and 11 as previously described.
It should be noted that the prime signal areas in the vehicle suspension are found to be dead center above and helow the center bearing point of the walking beams B and 14.
The walking beams are of course subject to considerabl~ stress caused by turning or parking of the vehicle or by flexing due to uneven ground or road surface. The prime signal area, that is to say, dead center above and below the center bear-ing point of the walking beams however is the point at which the unwanted signals cancel out and it is at this point the sensors must be located. As described heretofore, load cells and transducer means as previously employed in vehicle weigh-ing systems could not be rigidly secured to the prime signal areas owing to their large size and to the fact they could not be secured by conventional spot welding techniques.
Figure 4 is a side elevation view of a bogey as may be used with a railway flat car. In this case, there is a frame 17 which supports the flat car bed, and has an extension 18 extending therebelow. Linkage members 19 of well known construction couple axles 20 of wheels 21 to the frame extension 18. In a well known manner, therefore, the weight of the load carried on the flat car is extended through frame extension 18j linkage members 19, to the I ~ ~8~B 3 wheels 21.
It has been fo~ld that there is a line of maximum stress exhibited by the aforenoted members 19 by which the weight of the load is transferred to the wheels and strain gauges should be located along this line/ such as at points marked X. As heretofore described the strain gauges should be located centrally between the wheels if located on an axle and if on a walking beam such as the member 1~ should be located dead center either above or below a center bearing poin~.
Figure 5 is a si~e elevation of a vehicle suspen-sion system commonly known as the "~EKO"* four spring suspension.
In this case, the frame 49 is connected to the vehicle sus-pension by mounts 50, 51 and 52. A load equalizer 53 is pivoted on the mount 51 and springs 54 and 55 are connected between the load equalizer 53 and the mounts 50 and 52 respectively. Axles 56 are connected to the springs 54 and 55 in conventional fashion. The load cells and transducers as used in prior weighing systems eould not be used on the load equalizers in the "REKO" four spring suspension system, because of the size of the loa~ cells or~transducers. ~he strain gauge as used in the present system is of sufficiently small si2e that it can easily be welded directly to the load equalizer either above or below as indicated by the points marked X.
Figure 6 illustrates an air-bag suspension system wherein the frame 57 includes mounts 58 and 59~ Trailing arms 60 and 61 are connected pivotally to the mounts 58 and 59 at one end and are in engagement with their opposite ends with air-bags 62 and 63, the pressure in the air-bags 62 and 63 being equali~ed through line 64 as is common. Axles 65 and 66 are secured to trailing arms 60 and 61 in conventional fashion~
Trade Mark ; 3 The weight supported by axle 65 will of ~ourse be equal to ~he weight supported by axle 66 and therefore strain measured by strain gauges positioned a't the points X will be proportional to the weight of the vehicle.
Figure 7 illustrates a single axle vehicle and illustrates the frame 67 including mounts 68 and 69 with a spring 70 between the mounts to which axle 71 is connected in conventional fashion. In this embodiment pin 72,which extends through the eye of the spring 70 to connect the spring to mount 69 is in the orm of a special pin containing, integral to its construction, a pair o~ strain gauges. The pin and strain gauges are readily available commercially and since the weight of the vehicle frame 67 will be divided e~ually between mounts 68 and 69 ~he gauges at pin 72 will produce a signal proportional to the weight on the vehicle ~ra~e 67. Of course, it will be obvious that only one side of the suspension is illustrated in Figures 5, 6 and 7 in the interest of clarity and that in each case the opposite side would be identical to that illustrated.
~o Figure 8 shows in partly schematic and partly block diagram form the circuit portion of this invention.
A strain gauge 22 is connected as one arm of a Wheatstone bridge 23 which contains a balancing arm 24. The output signal of the Wheatstone bridge is detected in a differential amplifier,25, which preferably contains gain to boost the level of the signal.
The output signal of the differential amplifier 25 is applied through circuitry to be described below to an analog-to-digital converter 26, the output signal of which 3~ is applied to'a digital,display 27.

Accordingly, the strain exhibited from the prime signal area where the strain gauge is applied produces a digi-tal display which, by means of this invention, is calibrated in units of weight.
Of course, the output signal of the differential amplifier 25 may be applied to an analog display by which the degree of strain is exhibited as a reading on an analog meter.
In operation, the strain exhibited by the axle or 1~ other member to which the strain gauge is bonded causes changes in the resistance of the strain gauge. Since the strain gauge is located at one of the legs of Wheatstone bridge 23, upon changing of the resistance of $he gauge, t~e Wheatstone bridge is unbalanced, and an output voltage results which is sensed by the input to the differential amplifier 25.
The output signal of the differential amplifier is applied to analog-to-digital converter 26, which applies an appropriate signal to activate display 27.
The signal path of differential amplifier 25 to ~o the analog-to-digital converter 26 contains means for calibratin~
the unit. A first selecting means preferably comprising contacts 28, 29 and 30 is interposed, with contact 2S being connected to the output of di.fferential amplifier 25, contact 29 to a source of reference voltage, and moving contact 30 being connected to calibration potentiometer 31. The slide arm from potentiometer 31 is connected to the input o the analog-to-digital converter 26, and as may be seen, will pass a predetermined proportion of the signal applied thereacror-to the analog-to-digital converter 26.
3~ To calibrate the apparatus, moving contact 30 is caused to close the contact 28, as shown. The potent.iometer in balancing arm 24 is moved until the display reads 0.

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Should the display have read O prior to movement of the balancing arm, calibration potentiometer 31 should be moved so that i~s sliding arm is midway in its range, which will provide a random number output at display 27. The balancing arm 24 is then adjusted until the display reads O.
With a load applied, the bridge 23 will become unbalanced. F~r calibration, the load should be known, and with it applied, calibration potentiometer 31 is turned until the display reads the correct weight in whatever lo numerical units are desired, such as pounds, kilog~ams, etc.
The unit is now calibrated.
By switching contact 30 to break from contact 28 and make to contact 29, a reference voltage is now applied to the analog-to-digital converter ~6, which reference causes a number to be displayed on display 27. This number is now the calibration factor of the particular location of the strain gauge, and it should be recorded.
Should re-calibration be required due to a change in adjustment of potentiometer 31, the switch 30 is caused ~o to make to contact 29, and potentiometer 31 then varied so as to display the calibration number previously recorded on digital display 27. The unit will thus be in proper adjustment.
For instance, should the strain gauge 22 be one which is on the axle or load equalizer of a trailer, and the trailex is connected to the hauling truck, the operator need only look up the calibration number (which may be conveniently stenciled on a plate on the trailer), dial the number on cali-bration potentiometer 31, and his ùnit is now calibrated to record the weight o~ the trailer for which he has now calibrated 3~ his weighing unit. In this manner, a large variety of trailers can be pulled by the truck unit with very simple means for calibrating the weighing unit, and the load carried by the trailer can easily be read.
Of course with moving vehicles, since the load is distributed, there will be more than one sensor. For a truck of the type comprising the components shown in Figures 1 throug~ 7, there will be a number of s~rain gauges. The circuit of Figure 8 shows ~ow more than one straîn gauge is accommodated.
A circuit similar to the one described earlier is shown between the sensor and calibration potentiometer which is identical to the one described earlier, the reference 10 numerals carrying an "A" suffix, as in strain gauge 22A. A
switch 32 having a multiplicity of contacts 41, 42, 43, 44, and 45, and moving contact 46 is interposed between the respective calibration potentiometers and the analog-to-digital converter 26. The output signal derived from the moving contact of potentiometer 31 is connected to switch contact 41, the output signal derived from the moving contact of potentiometer 31A is connected to contact 42, and the output signals of other calibration potentiometers of other similar circuits connected to other sensors are respectively ~0 connected to other contacts 43, 44, etc. Moving contact 46 makes contact to the contact of the switch for which an output reading on the display 27 is desired, for calibration, and for reading of the weight supported by a particular axle. Besidès being a necessary information in case fines or tolls are to be levied on the basis of axle weight, this information is useful in order that the stress limit of the particular axle not be exceeded, or for the determination of the degree of imbalance or shifting which a particular load mi~ht exhibit. Calibration of additional circuits connected 3 to switch 32 is done in an identical manner as described earlier, with the known load per axle being initially carefully determined in order to obtain the calibration factors to be set up by each calibration potentiometer.

.' ' ' ' ' ' i L~ 3 .

It is also useful to obtain an overall load indication.
Accordingly, the output signals of the calibration potentiometers 31, 31A, etc. are applied to the input of a summing amplifier, which provides an output signal representative of the sum of all the output signals of each of the input circuits.
Connected to the output of the summing amplifier 47 is calibration potentiometer 48, the output from the slider thereof is connected to one of the contacts 45 of switch 32. Once calibrated in a manner similar to that described earlier, the operator need only switch contacts 46 to contact 45 and the display 27 will indicate the total weight carried by the vehicle.
While described above is a manner of displaying the gross weight of the entire vehicle and load ! since the weighing of the vehicle to establish the calibration will have included both the load and the vehicle weight, the unit can just as easily be calibrated to reflect weight of the load alone and the tare weight. Weighing of each axle associated with a particular strain gauge with the vehicle empty provides a calibration factor on the calibration controls based on a particular weight as measured on the weighing scale. This weight can be dialed on the display by means of the balance control, which position is noted. At any time, these calibration and balance control settings can be set, and a difference in the display weight reading will provide an indication o~ any changes in tare weight. Loads carried in excess of that will immediately be displayed on the display 27, either by associated axles as selected on switch 32, or in total with switch 32 made to contact 45.
It therefore is believed evident that this invention provides a simple and reproduceable manner of detexmining on an immediate basis the gross and tare weights of the vehicle . ~ , .

~ 1686b3 as loads are added and removed in a relatively simple manner for the operator of the vehicle. Furthermore, the weight is available immediately upon loading, with no necessity to travel to distant weighing scales, with the risk of exceeding road weight li~its or vehicle weight specified maxima. Each individual vehicle is also easily calibrated individually, which calibrations are easily checked and in case of tampering, are easily resettable.
In addition, no structural changes are required in the vehicle, and no flexible or levered mechanism need be added.
Further, in a multi-axle bogey system, as found in large commercial trucks or railway cars, a strain gauge at any of a number of key locations can provide a signal which may be calibrated to indicate total weight being supported by a number of bearing points. Consequently, an 18 wheel tractor-trailer unit can be measured accurately by five of such strain gauges, utiliz~ng the locations noted in the combinations of figures 1, 2 and 3. Further, by the use of the present invention a single tractor-trailer drive unit can be used to pull a large variety of trailers and directly read out the tare, gross, and load weights o~ the trailer and of the entire truck-trailer combination simply by modification of the calibration setting on the calibrate potentiometers. The weights can be read out by associated axle group or in total, at the option of the operator.
It should be noted that the positioning of the strain gauges at the prime signal areas indicated is o~ extreme importance so that unwanted signals such as those produced by turning of the vehicle, stress applied when the vehicle is parked on an incline or by the suspension flexing due to un-even ground, are cancelled out and so that the signal produced by the strain gauge is an accurate indication o~ the weight carried in the vehicle.

The weighing system as not~d can be used with other load-carrying or lifting machines other than vehicles.
Stationary or mobile cranes, walking beams, walking beam supports, spring hangers and shackles, body frames and members, axles, and axle housings all can carry the strain gauge using the circuit as described. In these cases, the strain gauges should be placed where the major force is exerted through the material to a support such as a wheel or track. This system clearly can be used on very large machines, .~o which cannot be handled by load cells.
As an example, where the strain gauge is attached to crane loaders or other lifting devices, the strain gauge or gauges are attached to the boom or lifting arms of suc~
machines whereby the weight of the material lifted can accurately be determined. This will allow running totals of material handled or the determination of whether design capacities are being exceeded. Overload or high-limit alarms can be generated by control circuitry of well known structure, using the si~nal pro~ided by this circuit as an ~O input. Since the strain gauges exhibit change in resistance due to molecular distortion, and since molecular distortion is a function of the strength of the material carrying the load, weakening due to structural failure of the boom or lifting arm can be made immediately apparent to the machine operator, and either manual or au~omatic shut-down of the machine, or operation at a reduced capacity, can be implemented in the interest of safety.
While the preferred manner of adhesion o~ the strain saugeis by spot welding of the strain gauge noted, it can also be bonded by other means such as by adhesives which faithfully reproduce the strain in the sensed material to the strain gauge.

1 16 ~ a 3 In another variation of the invention, a trailer to be pulled by a tractor drive unit and which'has a connector for transmitting the strain gauge signal contains an amplifier which isolates the strain gauge from the connector, and thus from the remainder of the circuitry within the drive unit.
An error sensing circuit compares the 'signal from the amplifier with'the signal on the cable connected ~o the strain gauge.
Should a change in the s~gnal occur at the connector due to moisture or leakage to ground, the gain of the amplifier is ~o increased to supply extra signal amplitude, thereby adjusting the cable signal to insure a correct reading.
This invention has therefore provided a significant advance in load measuring systems for vehicles and other load-carrying machines.
A person skilled in the art reading this specification may now conceive of other variations or embodiments. All are considered to be within the scope of this invention as defined in the appended claims.

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Claims (9)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. For use in a load-carrying vehicle, an in-board weighing apparatus comprising (a) means for detecting the variation in resistance of a strain gauge, (b) a bridge circuit having said means for detecting as a variable element, including a bridge balance control, for providing a strain output signal, (c) a source of reference potential, (d) first means for selecting alternatively the strain output signal or the reference potential, (e) a signal output display for indicating the strain in units of weight, and (f) an output level control connected between said means for selecting and the signal output display for setting the output display to zero when the reference potential has been selected by the selecting means.

2. A weighing apparatus as defined in claim 1, further including a plurality of means for detecting the variation in resistance of a plurality of strain gauges, individual bridge circuits each having one of said means for detecting as a variable element for providing individual strain output signals, said first means for being adapted for selecting alternatively the strain output signals or the reference potential, second means for selecting individual said ones of the alternatively selected strain output signals or the reference potential, individual output level controls connected in individual signal paths between the second means for selecting and the first means for selecting, the output level controls being adapted to allow the individual setting of a zero indication on the signal output display when each reference voltage is selected, the bridge balance controls being adapted to provide a predetermined indication on the signal output display when each of the individually selected ones of the strain output signals is selected.

3. A weighing apparatus as defined in claim 2, further including means having inputs connected to the outputs of each of the individual output level controls, a summing output level control connected to the output of the summing means which has its output connected, for selection, to said second means for selection.

4. A weighing apparatus as defined in claim 3 further including individual differential amplifiers connected between each of the bridge circuits and said first means for selecting, including means for increasing the amplitude of the output signal of the individual bridge circuits.

5. A weighing apparatus as defined in claim 4 in which the signal output display is a digital display, further including an analog to digital converter connected between the second means for selecting and the output display for translating the selected signal into a digital signal representative of the weight causing the corresponding detected strain gauge change in substance.

6. A weighing apparatus as defined in claim 1, 3 or 5, further including individual strain gauges connected to individual ones of said means for detecting, the strain gauges being welded to parts of a vehicle through which a load carried by the vehicle applies stress.

7. A weighing apparatus as defined in claim 1, 3 or 5, further including individual strain gauges connected to individual ones of said means for detecting, the vehicle comprising a steering axle and drive axles connected by a pair of walking beams, one strain gauge welded centrally to the upper or lower surface of the steering axle; and a pair of strain gauges each welded to the upper or lower surface, similarly to the strain gauge of the steering axle, of one of the walking beams, each centrally located on its walking beam between the drive axles at a prime signal area.

8. A weighing apparatus as defined in claim 1, 3 or 5, further including individual strain gauges connected to individual ones of said means for detecting, the vehicle comprising a wheel supporting frame and at least a pair of vehicle supporting wheels rotatably connected by linkage members to the frame; the frame and linkage members exhibiting points of major stress, and a strain gauge bonded to the frame or linkage member at a point of major stress.

9. A weighing apparatus as defined in claim 2 or 3 in which the first selecting means is comprised of multiple double throw switch means, each pole being connected to said individual output level controls! the second selecting means being comprised of a multi-contact switch, each contact being connected to the output of a respective individual output level control, the switch having a moving contact being connected in a circuit path to the signal output display.