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If the transducer value is not within the calibration range, the transducer will return to the
original reading. If the LID pressure value is within the allowed range (noted above), check
the voltage ratio of the transducer. To obtain the voltage ratio, divide the voltage (dc) input
from the transducer by the supply voltage signal, measured at the PSIO terminals J7-J34
and J7-J35. For example, the condenser transducer voltage input is measured at PSIO ter-
minals J7-1 and J7-2. The voltage ratio must be between 0.80 vdc and 0.11 vdc for the soft-
ware to allow calibration. Pressurize the transducer until the ratio is within range. Then
attempt calibration again.
4. A high pressure point can also be calibrated between 240 and 260 psig (1655 and
1793 kPa) by attaching a regulated 250 psig (1724 kPa) pressure (usually from a nitrogen
cylinder). The high pressure point can be calibrated by accessing the transducer on the
Status01 screen, highlighting the transducer, pressing the SELECT softkey, and then
increasing or decreasing the value to the exact pressure on the refrigerant gage. Press
ENTER to finish. High altitude locations must compensate the pressure so that the
temperature/pressure relationship is correct.
If the transducer reading returns to the previous value and the pressure is within the
allowed range, check the voltage ratio of the transducer. Refer to Step 3 above. The voltage
ratio for this high pressure calibration must be between 0.585 and 0.634 vdc to allow cali-
bration. Change the pressure at the transducer until the ratio is within the acceptable range.
Then attempt calibrate to the new pressure input.