DE3803241A1 - Programmable universal pulse transmitter with parameter-controlled adaptation to different measurement value pick ups - Google Patents

Abstract

The invention relates to a photoelectric pulse transmitter with an adaptation to different measurement value pick ups. Two light barriers 53, 55 and 54, 56 are provided which are arranged with a phase displacement and by which pulse sequences separated by the movement of a slotted disc 5 are supplied through electronic pulse shaping circuits 67A and 67B and subsequently via a logical combination and synchronisation stage 68 into a microprocessor 75. Parameters can be transmitted by means of a manually operable input module 99 via the microprocessor 75 into a separate storage module 76. The pulse sequences /TS and /KS processed by the microprocessor 75 are available at the output of output stages 96 and 97 as carrier signal sequence TS and control signal sequence KS to be fed to a central computer. Preferred use in tank data devices. <IMAGE>

Description

1. Need for a new development of the pulse generator

The use of today's photoelectric pulse generator is through the following disadvantages:

• - The necessary adjustment to the liquid counter is done via a mechanical transmission. Since a variety of brands are used there are many transmission variants in use. The adjustment of the still common is particularly problematic Gallons (US, Imperial Gallons ...) to the metric system.
• - Other variants arise because different impulses for Right and left rotation are required. This is through the order Installation of the locking mechanism rotated by 180 ° is achieved.
• - Furthermore, this role lock must be assigned to each pulse generator be, since the previous pulse generator neither recognize return pulses can still process, but a minimal return due to never excluded from bouncing processes in the hydraulic system can be.

The goal of all these disadvantages while maintaining high economic Avoiding advantages led to the development of a purely electronic pulse generator that allows various parameters freely programmable to adapt it to all variants to be able to.

The following parameters can be programmed with the new pulse generator, d. H. can also be changed on site at any time:

• - The division ratio can be with an accuracy of 4 decimal places be programmed in 1/10 000 steps and thus without gear (additional costs) to all liquid meters be adjusted.
• - The direction of rotation (CW, CCW) can be programmed so that the Roller lock can be omitted.
• - The maximum output frequency can also be programmed, d. H. the pulse generator can thus optimally connect to the following Price calculator, adjusted for quick evaluation will.

These parameters are in one, even without battery backup EE-PROM saved non-volatile.

Programming is done using the existing button module of the ER0, but could also be via the DIL switch or Thumb-wheal switches are done.

For calibration reasons, the device can be opened in the factory (open State) as often as required, but only once on site will.

In the case of a desired integration into the price calculator the parameters are displayed on the 7-segment display.

The function of the pulse generator is continuously monitored:

• - Constant review of the E-PROM content
• - Permanent function control of the processor by means of a watchdog circuit.
• - Permanent current control of the photo diodes of the light barrier.

If an error is detected, the fueling process is triggered by output three false impulses immediately interrupted. After that there is a reinitialization, followed by a new check both functions.

This ensures that the device can be checked without any outside - re-calibration, adjustment or zeroing - can work.  

2. Brief technical description

Using two light barriers (the signal between the two is over 90 ° phases shifted) a pulse disc with 125 slots (Light-dark ratio 1: 1) sampled.

A comparator circuit (pulse-pause ratio adjustable via potentiometer) forms the heavily worn impulses into rectangular impulses.

A hardware doubling is a frequency doubling the input pulse produces what is actually doubling corresponds to the number of slots on 250 slots.

In addition, the evaluation of the direction of rotation is made possible by this exor link significantly simplified by the software.

The signals of both light barriers are at 4 times the frequency the maximum speed sampled, d. H. the state of both Light barriers are detected, read into the computer and processed.

Synchronization is via the temporary storage in D-FF the light barriers are reached at the sampling frequency, d. H. all impulse changes low frequency are detected.

If a more frequent commute occurs, this is caused by the Synchronization suppressed, d. H. the synchronization ensures sufficient hysteresis with very high resolution of the angle of rotation.

Each time the processed signals are read in, the and evaluation by the software:

• - Test whether there is a pulse change:
  To do this, the previous state is buffered and compared with the current status of the pulse disk:
• - control calculation:
  It is checked whether a light barrier has failed and whether the max. Speed was exceeded. If this is the case, false impulses are output.
• - "Electronic gear":
  The number of input pulses is converted into output pulses (output in "real time") according to the division ratio. A corresponding calculation method results in a smaller rounding error than with the mech. Gear is given by the gear ratio.
• - Output:
  The signals are output in two channels with an exact phase shift of 90 °.
  This is achieved regardless of the output frequency by alternating output of edge changes on both channels.
  These output signals are raised to the potential of the supply voltage by means of a short-circuit proof transistor amplifier stage.

Each time the supply voltage is switched on, one occurs Initialization of the entire device, d. H. all parameters are reread.  

3. Optical scanning

In order to achieve a much higher resolution of the angle of rotation, the clock disc was designed with 125 slots.

This clock disc ( 5 ) is scanned according to Fig. 1 with two light barriers, which have a phase shift of 90 °.

In order to avoid an adjustment between the two light barriers, the diaphragm ( 4 ) is switched into the beam path, which has 2 × 3 slots with a phase shift of 90 °.

Item names:

1 carrier circuit board
2 PCB of the photo transistors
3 circuit board of the photodiodes
4 aperture
5 clock disc
6 steel beams (riveted with items 9 and 10 )
7/8 brass bolts
9. . . 12 brass sleeves
13/14 socket head screw M 2 × 8
25 carriers of the clock disk

4. Housing

In order to be able to comply with the provisions of explosion protection, the Device (clock disk, optical scanning and circuit board) in one Housing with flameproof encapsulation, which the Housing of the previous pulse generator will be very similar.

In order to be able to continue using the previous housing, in the light barrier can be accommodated. The evaluation circuit could then be in another room in the non-hazardous area Housing can be accommodated.  

5. Advantages of the new pulse generator

• - The new pulse generator is upward compatible with the previous one d. H. it can be used and sold without restriction.
• - The resolution of the angle of rotation of the drive axis was considerable improved.
• - The pulse generator has a 2-channel serial interface (for reasons of calibration accuracy), their level in height of the supply voltage are output. The two signals have an exact phase shift of 90 °.
• - Warehousing is reduced considerably because of the programming the parameter no variants arise.
• - Adaptation to new customers or new technical conditions can be done without development and time.
• - The signal output is short-circuit proof.
• - Constant checking of the function of the processor and immediate Interruption of the refueling process in the event of a malfunction.
• - The pulse generator is, beyond the use in the fuel pump, applicable wherever an angle of rotation in any pulse train Division is converted.
• - Another economic advantage would be the mechanical Replace totalizer with an electronic totalizer. This is easy with battery backup in the pulse generator can be implemented using an additional 2-wire interface to a display unit.

5.1 Realized technical data

• - Voltage range: 4.6. . . 15 V
• - Electricity:
  with 8748: 125 mA
  with 80C49: 45 mA (mask programmed µC)
• - speed n max. = 461.5 1 / min
• - Divider ratio: TV = 0.0000. . . 1.0000
• - Output frequency: fo max = 961 Hz
• - Resolution: angle of rotation γ min = 1 ° 26′24 ′ ′

6. Attachments

• - task
• - circuit diagram

Claims (1)

Photoelectric pulse generator with an adaptation to different transducers for converting measured values in the form of a rotary movement into signals for evaluation in legal-for-trade devices, the pulses being generated by the movement of a slotted disc in the beam path of two light barriers arranged out of phase, characterized in that each light barrier has a pulse shaping circuit Downstream for converting the sinusoidal signals emanating from the phototransistors into square wave signals is that the pulse shaping circuit is followed by a further module for the logical combination and synchronization of the two pulse sequences, the pulse sequences available on the output side are read into a processor, and an input module is provided for manual adjustment of parameters, the latter being captively storable in a separate memory module, and in that separate output stages are arranged on the output side of the processor for the B Providing a carrier signal sequence and a control signal sequence for feeding into a central computer unit.