Dc Voltage Checks; A/D Measurements - Omega 865 User Manual

5.4.1

DC VOLTAGE CHECKS

Using a precision digital voltmeter (DVM), make the following DC voltage checks in
Table 5-4:
Step
1
2
3
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.
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) =
DC VOLTAGE CHECKS
Item/Component
U102 pin 1 referenced
to pin 26
U102 pin 1 referenced
to pin 37
U102 pin 1 referenced
to pin 30
(Pin 31 voltage)-(Pin 30 voltage)
1000 x
(Pin 35 voltage)-(Pin 36 voltage)
TABLE 5-4
Required
Condition
>7.2V
+5V 1V
À3V
NOTE
12
Remarks
Battery Voltage
5V Power Supply