Application Note...

PCS400 Pressure Calibration System

Application:

Calibration of pressure transducers in new jet engine control modules

Challenge:

To provide a high accuracy absolute pressure calibration system with two pressure ranges and an internal barometer for single point calibrations. The manufacturer needed the capability to calibrate the pressure transducers in a variety of jet engine control modules (analog and digital) for both commercial and military applications. The control modules are installed on a variety of planes including the following: Airbus 320, 330 & 340 Military planes - F14, F16, F18, B1 & B2 Boeing 737, 747 & 777, regional jets and military helicopters.

Solution:

The dual range (with auto-switching) PCS400 was designed specifically for this type of application. The requirement was for two separate controllers – one low pressure unit with ranges of 30 psia and 150 psia and one high pressure unit with ranges of 150 psia and 795 psia. The internal barometric reference transducer was utilized to perform single point calibrations on the 30, 150 and 795 psia transducers in the PCS400. The PCS400’s are an integral part of a test system that includes computer, data acquisition equipment, temperature chamber and pressure console. The PCS400's are used to characterize the control module transducers at specific pressures and temperatures. A typical temperature range for these modules is 55 C to + 71 C. Modules are pressure tested at 5 to 10 pressure points depending upon the customer requirements. Some requirements check calibration both upscale and downscale. The PCS400’s communicate with the test computers over the IEEE (GPIB) port. All tests are automated and can be performed 24 hours a day. Reliability is very critical since the testing is unmanned and takes several hours to complete. One "glitch" in the calibration system can negate a long test run.