SU821963A1 - Device for measuring temperature sensor thermal inertia factor - Google Patents

Description

(54) DEVICE FOR MEASURING THE INDICATOR OF THERMAL INERTIA OF THERMAL SENSORS

Figure 1 presents the block diagram of the device; 2 shows timing diagrams for his work.

The device contains a heating source of a thermal sensor with a control unit 1, a controlled thermal sensor 2, a divider-3 reference voltage source 4, an amplifier 5, two circuits b and 7 comparisons, two triggers 8 and 9, a time demodulator 10, an integrator 11 Dual controlled keys K and, the corrective link 12 with a controlled constant time and the recorder 13.

The device works as follows.

According to the signal from control unit 1, the monitored temperature sensor 2 is turned on for short-term preheating for which the recorder 13 is blocked. After switching to the cooling mode of the temperature sensor 2, unit 1 sets the trigger 8 to the initial zero state, at which its output voltage closes the switch K and opens the key of the integrator 11. The output voltage of the integrator 11 is then set at a zero level (FIG. 2 d).

When the temperature sensor 2 cools down, its output voltage, amplified by amplifier 5, is changed according to the law of FIG.

UgW-U e-.), .1 /

where Yc is the initial value of the exponent) t is the thermistor probe

UnW voltage disturbance.

With the help of schemes b and 7 of comparison, the moments of time t and t, respectively, are fixed, at which the output voltage and 5 (t) reaches some reference levels. ,, S KM) / which are set by the source 4 of the reference voltage and divider 3. At time t, comparison circuit 7 is activated and with its output signal triggers 9 into one state, which lasts until time i2 / when comparison circuit B operates, returning the trigger 9 to the zero state. The time interval D1o during which the trigger 9 is in the immediate state is determined by the dependency (Fig. 2b), 1 ,,

 H ... r2 uj-unlt l

The time interval At the time demodulator 10 is converted to a voltage proportional to the value of the PTI temperature sensor, which controls the value of the constant time of the corrective element 12.

The described path for determining the value of the ICD of the thermal sensor 2 serves to adjust the time constant of the correction link 12 and therefore to it

High accuracy and noise immunity are not required.

The main measurement path of the PTI temperature sensors consists of the trigger 8, the Integrator 11 and the correction link 12. At the time t2, the output signal of the comparison circuit 6 translates the trigger 8 into a single state (Fig. 2c). The output voltage of the trigger 8 opens the key K2 and the circuit. .kata key K of integrator 11. The output voltage of amplifier 5 through a closed key K is fed to the input of integrator 11. As a result, starting from time 1.2 / the output voltage of the integrator changes according to the law (Fig. 2d)

and ,, e% unw di

and.

.f,

-P

n RC

Where

- constant of the integrator time 11j

yp

- average interference voltage.

In practice, in many cases, the interference is a stationary random process with zero mean value (). Thus, the steady-state value of the output voltage of the integrator is equal to

 r U11 - proportional to the measured value of L.

Integrator output voltage

11 changes incrementally with time constant t. In order to quickly obtain a steady-state U value, the output voltage of the integrator 11 enters

on the corrective link 12, the time constant of which j in the first approximation is equal to the measured value of PTI. At the output of the corrective element 12, the voltage is changed by the law

and „H1 ... (.,

where OS is the correction factor of the corrective element 12 (figd).

Since СХ.Л1,, the output voltage of the corrective element

12 reaches a steady-state value proportional to the measured value of temperature sensor 2, much faster than the output voltage of the integrator 11. Therefore, in terms of speed, the proposed device is not inferior to the known one. At the same time, due to the presence of noise and pickup in the measuring path of the integrator 11 contained in the output signal the temperature sensor 2 is smoothed by the integrator 11 and, therefore, the measurement result has little effect.

Claims (2)

1. USSR author's certificate number 525862, cl. G 01 K 15/00, 1975. 2. USSR author's certificate № 62412,3, cl. G 01 K 15/00, 11.04.77 (prototype). t h