Inspection method of absolute pressure transmitter:
1. Record the atmospheric pressure value, assuming it is A (kPa), the measurement range is 0~B (kPa), 24VDC, output 4~20mA
2. Calculation method of output current:
Changes in output current caused by changes in atmospheric pressure: [(A-100kPa)/B] × (20-4)
The output current at each pressure value should be the corresponding theoretical value plus [(A-100kPa)/B]×(20-4), which is the theoretical value under the current atmospheric pressure. For example, the current atmospheric pressure is 101.5kPa, the measurement range is 0~400kPa, and the output signal is 4~20mA:
Changes in output current: [(A-100kPa)/B]×(20-4)= [(101.5-100kPa)/400]×(20-4)=0.06mA
Therefore, 0.06mA is added to the theoretical value of each test point:
Pressure value (kPa) 10 100 200 300 400
Output current value 4.460 8.060 12.060 16.060 20.060
Note: The output current at 10kPa is calculated as follows,
4 mA+〔(10/400)×(20-4)〕+0.060 mA=4+ 0.4+ 0.060= 4.460 mA
3. Assume that the current atmospheric pressure is 101.0 (kPa), the measurement range is 0~200 (kPa), 24VDC, and the output is 0~5V, then:
Change in output voltage: [(A-100kPa)/B]×(5V-0V)= [(101-100kPa)/200]×(5-0)=0.025V
Therefore, 0.025V is added to the theoretical value of each test point:
Pressure value (kPa) 10 50 100 150 200
Output voltage value (V) 0.275 2.025 3.025 4.025 5.025
Note: The output current at 10 kPa is calculated as follows,
[(10/200)×(5-0)]+0.025 V= 0.25+ 0.025= 0.275 V