Omega 871A, Руководство пользователя

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3. Plug in the miniature connector to input TC1 of the Model 872A.
4. Connect the copper wires to the 100:1 divider (see Figure 4-3) with the
iron wire connected through the 1.98 kilohm resistor, to the dc calibra-
tor positive terminal.
5. Prepare a distilled water bath as outlined in paragraph 4.2.3, step 5.
*The 20
Ω
resistor must be held at a uniform
temperature during calibration.
Figure 4-3. Calibration Setup for Model 872A
4.3.4 Calibration Procedure
It is not necessary to disassemble the case for calibration. All adjustments
are accessible by removing the covers shown in Figure 4.2.
1. Remove the battery and trimmer compartment covers from the Model
872A.
2. Turn the Model 872A on and perform the calibration adjustments listed
in Table 4-4.
TABLE 4-4
CALIBRATION ADJUSTMENTS FOR MODEL 872A
9
872A Calibrator Trimmer Desired
Step Adjustment Range Setting (V) Adjust Reading
1 Input Offset Null 200ºC 0.0000 R109 00.0ºC
2 + Gain (X1) 760ºC 4.2922 R104 760ºC
3 + Gain (X10) 200ºC 1.02217 R105 190.0ºC
4 - Gain 200ºC -.19604 R103 -40.0ºC
5 ºF Offset 200ºF 0.000 R102 32.0ºF
12
4.5.1 DC Voltage Checks For Model 871A
1. Battery: VBAT > 7 V
2. Power Supplies:
V + to (Analog Ground) = +2.8 ± 0.4 V
V + to (Digital Ground) = +5 ± 1 V
3. Reference Diode: CR101 to (Analog Ground) = -1.23 ± 0.03 V
4. Negative Reference Divider: (Reference to Analog Ground)
R119
Pin mV* Pin mV* Pin mV*
2 -210 5 -204 8 -195
3 -209 6 -199 9 -186
4 -204 7 -198 10 -173
*The setting of R104 and the tolerances of the resistors within the network
(R119) can affect these levels by ± 5%.
5. Deintegrate Comparators:
U103A PIN 3 to = 150 ±25mV
U103B, PIN 6 to = -150 ± 25 mV
6. Cold Junction Voltage:
(Ambient temperature 25º ±3ºC)
-COM to
= 1.0 ±0.6 mV
4.5.2 DC Voltage Checks For Model 872A
1. Battery: VBAT > 7 V
2. Power Supplies:
V + to (Analog Ground) = +2.8 ± 0.4 V
V + to (Digital Ground) = +5 + 1 V
3. Reference Diode: CR101 to (Analog Ground)= -1.23 ±0.03 V
4. Negative Reference Divider: (Reference to Analog Ground)
R119
Pin mV* Pin mV* Pin mV*
2 -312 5 -274 8 -267
3 -293 6 -272 9 -254
4 -277 7 -271 10 -242
*The setting of R104 and the tolerances of the resistors within the network
(R119) can affect these levels by ±5%.
5. Deintegrate Comparators:
U103, Pin 3 to =190 ±30 mV
U103B, Pin 6 to = -180 ±30 mV
6. Cold Junction Voltage:
(Ambient temperature 25º ±3ºC)
-COM to
= 1.3 mV ±0.6
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