how to consider tolerance in process design

[jumacao]

How instruments tolerance affect system process? If I have a range of 45 to 55 and want to measure up to 0.1. What instrument do I need (tolerance???)?

 

[gr2vessels]

Depending on what's your problem, for a range between 45 and 55 mm, you need either a caliper or stronger glasses. Perhaps an electronic pyrometer with digital read-out, if you measure temperature. Any clock will do for time measurement between 45 and 55 years of age. By the way, what do you measure?
cheers,
gr2vessels

 

[ayoyo]

depend on your process parameter setting as well. If you need to measure up to one decimal point, you can specify it in your instrument data sheet that measurement accuracy up to 0.1 decimal point, and let the instrument supplier to the recommendation, or you can go to their website to find out the accuracy for the instrument that you need. Normally, one decimal point should be no problem for temperature,pressure... but for composition analyser, such as H2S concentration, decimal point will affect your cost very much.

 

[JLSeagull]

For pressure based instruments, the latest model transmitters are very accurate. My preferred manufacturer offers a standard and ultra accuracy selection (0.025% of span). Using ultra, many engineers select the 0-1000 inch water range from one manufacturer for any range required above 0.5 inches of water (12.5 mbar to 2.5 bar). This transmitter could be calibrated 45 to 55 inches of water. The ultra accuracy is not available in all ranges so the acccuracy for the model suitable for 45 to 55 bar might be 0.055% span.

This pressure example cannot be extended to temperature rangeability.

 

[jumacao]

I am measuring temperature

 

[ayoyo]

i think measuring temperature range 45.0 to 55.0 deg C should be no problem for most temperature sensor, either thermocouple, RTD, ...
To be sure, you can consult instrument engineer or ask your supplier.

You can download instrument specification from website to check their measurement accuracy as well. Try E&H.

https://portal.endress.com/wa001/dla/50001928225/000/01/TI257ten_0808.pdf

I hope this is what you are looking for.