A kind of high precision measuring temperature module that is applied to calorimeter
Technical field
The utility model relates to the calorimeter electronic manufacturing field, and in particular, the utility model is about reducing a kind of high precision measuring temperature module that is applied to calorimeter of calorimeter electricity manufacturing cost.
Background technology
Calorimeter is a kind ofly to be used to measure and to show that current discharge or absorb the instrument of thermal energy through heat-exchange system, are widely used in the heat metering of northern China.In calorimeter when work,, the supply and return water temperature signal that flow that provides according to flow sensor and temperature sensor provide, and the time of current warp calculate and show the thermal energy that this system discharges or absorbs by counter.
Calorimeter can be divided into two big modules by its major function: temperature measurement module and flow measurement module.When having only the equal error in dipping of these two modules all to meet the demands, the thermal energy accuracy of measuring of calorimeter just can be guaranteed, and therefore, high-precision thermometric seems most important in the application of calorimeter.
Include temperature sensor and counter in the temperature measurement module, usually adopt platinum sensor in the calorimeter as temperature sensor, the resistance value of platinum sensor changes along with variation of temperature, and the two is generally linear, if can obtain the resistance value of platinum sensor, then can be by the current temperature value of the anti-release of counter.
Calorimeter in the market adopts numeric type temperature measurement module cost height, is unfavorable for using in the product for civilian use, therefore needs a kind of low temperature measurement module of accuracy of detection height, cost that is applicable to civil heat meter.
Patent Office of the People's Republic of China has announced a CN2413269Y document January 3 calendar year 2001, name is called calorimeter, this calorimeter is made up of water meter, temperature probe, signal processing circuit, display, is characterized in, is built-in with digital temperature probe in water inlet and water return pipeline; Display and test section partial installation; In display, keep two magnetic induction buttons.Since adopted digital temperature probe, therefore, good stability, temperature-measuring range is wide, the precision height; Display and test section partial installation and be loaded on outdoor, and built-in magnetic induction button, the small magnet that it and meter reading personnel hold matches, making needs information to access at any time, is convenient to check meter and checks whether robber's thermal phenomenon is arranged.This calorimeter adopts digital temperature probe, and cost is higher, is unfavorable for that the product for civilian use uses.
Summary of the invention
The utility model is for solving the shortcoming that the temperature measurement module cost that exists in the prior art and accuracy of detection can not be taken into account, and a kind of have accuracy of detection height, the high precision measuring temperature module that is applied to calorimeter that cost is low are provided.
The technical scheme that its technical matters that solves the utility model adopts is: the utility model comprises temperature measurement circuit, control module and timing unit, and temperature measurement circuit links to each other with control module, and control module links to each other with timing unit; Temperature measurement circuit comprises resistance 1, electric capacity 2, constant current source 3, temperature sensor 4, comparer 5, one end of resistance 1 links to each other with control module, the other end of resistance 1 links to each other with an end of electric capacity 2, the positive input terminal of comparer 5 respectively, the other end of electric capacity 2 links to each other with ground, after constant current source 3 and temperature sensor 4 are in parallel, one end links to each other with ground, and the other end links to each other with the negative input end of comparer 5, and the output terminal of comparer 5 links to each other with control module.When comparer 5 output low levels, control module controlling resistance 1 is to electric capacity 2 chargings, when comparer 5 output high level, 2 discharges of 1 pair of electric capacity of control module controlling resistance in the timing T of timer, are write down the T.T. T1 of resistance 1 to electric capacity 2 chargings by timer, because temperature sensor 4 both end voltage Vref are directly proportional with duration of charging T1, therefore can get the magnitude of voltage of Vref, can calculate the resistance value of temperature sensor 4 according to Ohm law, thereby can extrapolate temperature value.
As preferably, temperature sensor 4 is platinum sensors.Platinum sensor has the advantage of accuracy of detection height, good stability.
As preferably, resistance 1 is that low temperature floats precision resister.Low temperature floats the stability that precision resister can guarantee thermometric.
As preferably, control module comprises controller 6, and controller 6 is microprocessors.Microprocessor has the advantage that cost is low, function is complete.
As preferably, timing unit comprises timer 8, timer 7, and timer 8, timer 7 link to each other with control module respectively.Can adopt ready-made timer and timer, thus simplified design.
The beneficial effects of the utility model are: compared with prior art, the utility model has saved small signal amplification circuit, thereby has reduced cost, has realized a kind of high precision of calorimeter, thermometry cheaply of being applied to; Because controller, timer and timer can be integrated in the single-chip microcomputer usually, therefore, this temperature measurement module circuit is simple, cost is low, and the temperature measurement accuracy height.
Description of drawings
Fig. 1 is a kind of structural representation that the utility model is applied to the high precision measuring temperature module of calorimeter.
Among the figure: 1. resistance, 2. electric capacity, 3 constant current sources, 4 temperature sensors, 5 comparers, 6 controllers, 7 timers, 8 timers.
Embodiment
Below by specific embodiment, and in conjunction with the accompanying drawings the technical solution of the utility model is described in further detail.
Embodiment:
A kind of high precision measuring temperature module that is applied to calorimeter of present embodiment, referring to Fig. 1, comprise temperature measurement circuit, control module, timing unit, temperature measurement circuit links to each other with control module, control module links to each other with timing unit, temperature measurement circuit comprises resistance 1, electric capacity 2, constant current source 3, temperature sensor 4, comparer 5, one end of resistance 1 links to each other with control module, the other end of resistance 1 respectively with an end of electric capacity 2, the positive input terminal of comparer 5 links to each other, the other end of electric capacity 2 links to each other with ground, and after constant current source 3 and temperature sensor 4 were in parallel, an end linked to each other with ground, the other end links to each other with the negative input end of comparer 5, and the output terminal of comparer 5 links to each other with control module.Control module comprises controller 6, and controller 6 adopts microprocessor.
When initial, the P1 of controller 6 end output low level, the output end vo ut of comparer 5 is a low level, the temperature detection step is as follows:
1, the P1 of controller 6 end output high level, this moment, electric current was flowed through resistance 1 to electric capacity 2 chargings, as voltage Vin during greater than Vref, Vout is a high level, this moment opening timing device 8 and timing T.
2, the P1 of controller 6 end output low level, this moment, electric capacity 2 was in discharge condition, and as voltage Vin during less than Vref, Vout is a low level.
3, the P1 of controller 6 end output high level is opened timer 7 simultaneously and is picked up counting, and this moment, electric capacity 2 was in charged state, and as voltage Vin during greater than Vref, Vout is a high level, and this moment, timer 7 stopped timing, and was t1 between clocking.
4, repeating step 2,3, until the timing T that arrives timer 8.
5, the P1 of controller 6 end output low level, measuring process finishes.
If when T time internal timer 7 amounts to n time, the 1st time timing time is t1, the n time timing time is tn, then total charging time: T1=t1+t2+t3+ ... + tn.
Because the Vin terminal voltage fluctuates among a small circle round Vref in the measuring process, can be similar to and think that Vin voltage remains unchanged, so the charge volume of electric capacity 2 equals discharge electricity amount, then have:
(1)
Q1: total charge capacity
Q2: total discharge electricity amount
(2)
I1: charging current
I2: discharge current
T1: total charging time
T: thermometric T.T.
Vcc: supply voltage
Vin: electric capacity 2 both end voltage
R1: resistance 1 resistance
Can get by formula (1) (2) (3):
By (4) as can be known, under the certain situation of thermometric T.T. T and power source voltage Vcc, electric capacity 2 both end voltage Vin are directly proportional with total charging time T1, because the Vin terminal voltage fluctuates among a small circle round Vref in the measuring process, can be similar to and think that Vin voltage equals Vref, then has:
Because the existence of constant current source 3, the electric current of the temperature sensor of flowing through is always I, then has:
According to (4) (5) (6), then have:
The resistance value of temperature sensor 4 can be calculated by formula (7), thereby temperature value can be extrapolated.
Because temperature sensor 4 both end voltage Vref are directly proportional with duration of charging T1, therefore can get the magnitude of voltage of Vref, the resistance value of temperature sensor can be calculated according to Ohm law, thereby temperature value can be extrapolated.
Above embodiment is one of preferred plan of the present utility model, is not that the utility model is done any pro forma restriction, also has other variant and remodeling under the prerequisite that does not exceed the technical scheme that claim puts down in writing.