Question

I have received my Endevco pressure transducer with the calibration certificate. I am uncertain of the terms listed on the cal cert. Can you explain these terms a little more relative to how it may affect my usage of the transducer?

Endevco Pressure Transducer Test Report Certificate

Answer

The terms listed below are the key terms on the cal cert that are not self-explanatory, i.e., range, sensitivity, excitation, input/output resistance, etc. It should be noted that IM8500 will have much more detailed information about Endevco's pressure transducers' design and performance capabilities. See below a sample calibration certificate and an explanation of the associated terms previously referenced.

1. Zero Pressure Output - This is also known as ZMO (zero Measurand output). This is the output of the pressure transducer on the green and white wires with no pressure applied, excitation voltage applied, and at 75° F. The output can be either positive or negative, depending on how MSS-OC performed the temperature calibration/compensation.

2. Full Scale Output - This is the output of the transducer with the model's pressure range applied. Depending on the model, the maximum rated pressure is 2.5 to 3 times the pressure range. This measurement is also performed at 75° F.

3. Non-linearity - This is a calculation using the Best Fit Slope Line (BFSL) method to determine the largest deviation on the pressure output when compared to the full scale output at 75° F. The pressure output is measured from 0 PSI to full scale pressure in 20% pressure increments.

4. Hysteresis - This is a measurement of the shift/difference if value of the ZMO at 75° F before and after the minimum and maximum operational temperature. This tests the temperature stability of the sensor die.

5. Non-repeatability - This is the largest deviation of the measured output in 20% pressure increments from 0 PSI to full operating pressure between 2 cycles of the pressure increments. This is measured at 75° F. (For example, the output is measured at 75° F at 0, 0.2. 0.4. 0.6, 0.8, & 1.0 PSI. The pressure is returned to 0 PSI and the measurements are repeated at the same pressure increments for the second cycle. The output at each pressure level from the 1st cycle is compared to the 2nd cycle. The pressure level with the largest difference is used to determine the non-repeatability value.

6. Combined Lin., Hyst. & Rep - an RSS value from the - 3 values collected from 3, 4 and 5 above. The calculation is the Square root of ((Non-linearity x Non-linearity) + (Hysteresis x Hysteresis) + (Non-repeatability x Non-repeatability)). Note: Non-linearity has the largest effect on this calculation.

7. Thermal Zero Shift - This is the amount of shift allowed to the ZMO in the 200° operational temperature span as a percentage of the full scale output

8. Zero Shift - This is the limit the ZMO is allowed to change after the unit has been subjected to maximum rated pressure (2.5 or 3X operational pressure range). This is a calculation of the ZMO shift in reference to the full scale output.

9. Thermal sensitivity shift - This is the limit the sensitivity (full scale output - ZMO) is allowed to shift over the 200° operational temperature span. The sensitivity is measured at the minimum and maximum operational temperature, the difference is then compared to the overall device sensitivity. The calculated value cannot exceed the maximum value specified on the performance specification, typically 4%.