AMS 2750E - Digital Instrument Calibration Accuracy Requirements

[Dr_bld]

Hello, I have a question regarding digital instruments calibration accuracy.

In our company we have new device (cryo chamber) for deep freezing and tempering. Class 2, Instrumentation type B. Temperature controller as well as over-temperature controllers (2 instruments for min and max temperature) have accuracy of 1 degC. According to AMS 2750E Table 3 note 4, the sensitivity of those instruments is correct. However, in the Table 3 in line “Digital instrument” it is stated that those instruments have to be calibrated with accuracy of ± 2 degF (±1.1 degC). For our processes we use Celsius scales that means that we have to calibrate our instruments with accuracy of </SPAN>±1.1 oC. According to that all of instrument have to operate with accuracy of 0,1 degC. Is my way of understanding of AMS2750E standard correct? I my point of view our instrumentation do not meet standards requirement.

Is it allowed to change the calibration accuracy to 1 degC (make it more restrict, but with lower accuracy)?

 

[dwperron]

If I understand correctly, you have a controller that you calibrate to 1°C accuracy. The Table 3 minimum accuracy requirement for your controller would be no less than ±1.1 °C, so your controller meets the minimum accuracy requirement. No problem there.

As for changing your calibration accuracy to 1 °C, in the heading for Table 3 under Calibration Accuracy it refers to Note (1) which reads "Instruments of equivalent or greater accuracy are acceptable" so you are fine there.