12
Step
Item/Component
Required Remarks
Condition
1
U102 pin 1 referenced
>7.2V
Battery Voltage
to pin 26
2
U102 pin 1 referenced
+5V
6
1V
5V Power Supply
to pin 37
3
U102 pin 1 referenced
À
3V
to pin 30
TABLE 5-4
DC VOLTAGE CHECKS
5.4.2 A/D
MEASUREMENTS
To verify that the A/D and associated circuitry are operating properly, measure the four
voltage points. Use the following formula to calculate the display reading.
1. Place a stable input to the instrument under test. For example, 190°F for the Model
865 and 150°C for the Model 866.
NOTE
All the measurements in steps 2 through 5 are referenced to
analog common.
2. Measure the voltage at U102 pin 31 (IN HI) and record the value.
3. Measure the voltage at U102 pin 30 (IN LO) and record the value.
4. Measure the voltage at U102 pin 35 (REF LO) and record the value.
5. Measure the voltage at U102 pin 36 (REF HI) and record the value.
6. Calculate the display reading using the measured voltages and the following formula;
Display Reading (disregarding decimal point) =
1000 x
(Pin 31 voltage)-(Pin 30 voltage)
(Pin 35 voltage)-(Pin 36 voltage)
5.4.1
DC VOLTAGE CHECKS
Using a precision digital voltmeter (DVM), make the following DC voltage checks in
Table 5-4:
Summary of Contents for 865
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