Rockwell Automation 1414-IPZxxxxx_CPZxxxxx_CPDxxxxx Differential Air Pressure Transmitter - Manual (Page 8)

8
Differential Air-pressure Transmitter
Publication 1414-IN011B-EN-P - July 2010
4. Allow the transmitter to warm-up for several minutes before attempting to verify the
device accuracy or adjust the null offset.
The module uses a sophisticated temperature compensation circuit to ensure maximum
accuracy of the device. It is best to allow the transmitter to operate for one hour before
any adjustment or calibration is performed.
5. Verify proper operation by measuring the output signal.
•
For voltage output configuration, measure the voltage between the OUT and COM
terminals. The voltmeter should read between 0…5V DC or 0…10V DC depending
on the output range selected.
•
For current output configuration, insert a mA meter in series with the OUT
terminal. The mA meter should read between 4…20 mA.
Operation
If the module is set to a unipolar range such as 0…2 in. wc, then the pressure applied to the High
port must be higher than the pressure applied to the Low port. In this case, if the Low port is left
open to ambient pressure and the High port is used to measure a positive pressure, then the
output pressure can be calculated as follows:
•
4…20 mA Pressure = [(Output current – 4 mA) / 16 mA] x Range
•
0…5V DC Pressure = (Output voltage / 5 V) x Range
•
0…10V DC Pressure = (Output voltage / 10 V) x Range
In the case of 0… 2 in. wc, 4 mA or 0 V = 0 in. wc, and 20 mA or 5 V or 10 V = 2 in. wc. Since the
transmitter is linear, 1 in. wc would be 12 mA or 2.5 V or 5 V.
If the positive pressure connection is reversed then the transmitter will always output
4 mA or 0 V.
If the module is set to a bipolar range such as ±2 in. wc, then the pressure applied to the High
port should be higher than the pressure applied to the Low port for a positive output response. In
this case, differential pressure can be measured using both ports. If the High port has a positive
pressure with respect to the Low port, then the output indicates a positive pressure. Negative
pressure is indicated if the High pressure is less than the Low pressure. For bipolar ranges, the
output pressure can be calculated as follows:
•
4…20 mA Pressure = [(Output current – 4 mA) / 16 mA] x 2 x Range – Offset
•
0…5V DC Pressure = (Output voltage / 5 V) x 2 x Range – Offset
•
0…10V DC Pressure = (Output voltage / 10 V) x 2 x Range – Offset
In the case of ±2 in. wc, 4 mA or 0 V = -2 in. wc and 20 mA or 5 V or 10 V = +2 in. wc. Since the
transmitter is linear, 0 in. wc would be 12 mA or 2.5 V or 5 V.