6. Connect a short circuit across the 1K resistor and place the RANGE SELECTOR in the X0.01 position. Adjust
the COARSE zero control. It should be possible to adjust this control ± 40% of full scale.
CONNECTOR PIN
VOLTAGE
FUNCTION
13
+12 to +13
SENSOR ELECTRONICS
SUPPLY VOLTAGE
14
+12 to +13
SYSTEM CHECK COMMAND
15
6V RMS
EXCITATION VOLTAGE
TEST B
LOCALIZING MALFUNCTIONS TO ELECTRONICS UNITS
1. Disconnect the sensor cable from the 270 and check voltages at the sensor connector.
(Reference VOM to pin 2)
ELECTRONICS UNIT VOLTAGE CHECKS
2. Repeat step 5 of TEST A at the sensor connector. Results should be the same.
RECALIBRATION
Whenever components have been replaced in the 270 it is necessary to perform the following calibration check.
1. Adjust the NULL for a zero setting.
2. Place the DIPSLAY UNITS SELECTOR in the mmHg position.
3. Switch the RANGE SELECTOR to the F.S. position and adjust for +10000 ± 0.01% (100000 for a 270-5)
Should the problem be traced to the 270 unit, it can be troubleshot by placing the RANGE
SELECTOR in the F.S. position for signal tracing purposes. The proper voltage levels
and waveforms are included on the schematic. To properly synchronize an oscilloscope
for signal tracing, trigger it externally from the oscillator output. Trigger shall be set
for a positive slope. The power supplies are separated from their loads by jumpers which
may be removed for test purposes.
CAUTION!!
All supplies should be disconnected
at the same time. Damage to the unit may occur if one supply is disconnected while
the others are connected to the circuit.
5-3
