RADIOMETER TCM3 - Page 66

2. TCM3 TCM3 and TCM30 Service Manual
Analog PCB, continued
A/D Conversion The nominal duty cycle d (R44 in mid-position) can be expressed as follows:
inued)
(continued) R50 R50 R48
d=-Vin* +(1+ )*
5*(05*R444R45) © 0.5*R44+R45° R47+R48
The frequency of the D-FF Q-output: f=d * fuck
The table below lists the duty cycle and frequency as a function of some typical
input signals.
MUX channel | Input Signal TP6 Duty-cycle | Frequency
0 (0002) +1 mV -0.684 V 0.1863 18.63 kHz
+185 mV -3.388 V 0.7267 72.67 kHz
1 (02) -1 mV -1mV 0.0499 4.99 kHz
-185 mV -185 mV 0.0867 8.67 kHz
-40V -40V 0.8489 84.89 kHz
2 (Pol. voit.) -680 mV -680 mV 0.1855 18.55 kHz
3 (Therm. 2) 37°C 27V 0.5891 58.91 kHz
45°C -35V 0.7490 74.90 KHz
4 (Therm. 1) 37 °C ov 0.0497 4.97 kHz
45 °C -40V 0.8489 84.89 kHz
5 (Унвлт) -14.7 V -4.69 V 0.9878 98.78 kHz
-118V -3.53 V 0.7548 75.48 kHz
6 06242 50 mA -1.00V 0.2495 24.95 kHz
OmA ον 0.0497 4.97 kHz
7 (Ground) 0 0 0.0497 4.97 kHz
The duty cycle d of A/D converter 2 can be expressed:
R60 R60,, R58
+(1+ 二 一 )* 一 一 一 一
5*R55 * R55 RS8+RS7
For thermistor 1 = 37 °C, d= 0.0498, f= 4.98 kHz
For thermistor 1 = 45 °C, d =0.8498, f= 84.98 kHz
d=-Vin*
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