Analysing analog input from a diameter gauge with 1 micron accuracy !!!!

rajesh_gklm · Nov 30, 2009

Hey Friends

I am using EZTouch PLC. I am trying to connect with a diameter gauge of 1 micron accuracy through an analog input module. The output of gauge in terms of voltage and the range is 0-10v. The resolution of analog input module is 12bit. Can i get this 1 micron change of product through this analog module????

i am a beginner and sorry ,if the question is foolish!!!!!!!!

OZEE · Nov 30, 2009

Tell us more about your gauge.

rdrast · Nov 30, 2009

IF your analog input module is unipolar (positive only), and IF your gauge maximum OD is 0.4096 cm, then yes, you can measure down to the micron level. However, the analog input will probably still experience conversion jitter, reducing accuracy.

If the analog input is bi-polar, then the maximum OD (at 10VDC) can be only 0.2048 cm.

The accuracy will also depend on the dynamic range of the analog output of the gauge head, and the calibration specifications on the input module.

JeffKiper · Nov 30, 2009

As the 2 GURUs have state you need to provide more info on your sensor. I have tried this before with several different manufacture gauges/ sensors. I have gotten marginal at bestresults with the lower end less than $5K. The sensor needs to measure sub-micron in order for you te get a good reading. If the resolution of you sensor is +/- 2 microns then no you will never get 1 micron reading that mean anything.

rajesh_gklm · Dec 1, 2009

Gauge Spec

Thank You for all
The Gauge specification is given below

Measuring axis
Single axis
Measuring gate
59mm by 59mm
Measurement range
0.2 to 50mm
Measurement error at an ambient temperature of 20C:
Object at the centre of the gate < +/-1.5micro m +/- 0.008%.
Object >0.5mm anywhere within the gate < +/-4 micro m +/- 0.016%.
Temperature coefficient of measurement
< [+/-0.05 micro m – 0.001%] per degree C over the range +5 to +45 degree C.
Scan [measurement] rate
600Hz.
Measurement jitter:
Scan to scan < 6 micro m + 0.1%
Block of 8 scans to block of 8 scans < 1.5 micro m + 0.05%
Block of 80 scans to block of 80 scans < 0.7 micro m + 0.01%
FFT residual results, typical:
The results are not zero for a constant sample diameter due to measurement errors;
typical results are given below.
At a 600Hz sample rate, maximum amplitude for any frequency up to one quarter of
the sample rate = 0.6 micro m + 0.02%
At a 30Hz sample rate, maximum amplitude for any frequency up to one quarter of
the sample rate = 0.4 micro m + 0.01%
SPC residual results, typical:
The results are not zero for a constant sample diameter due to measurement errors;
typical results are given below for a 10s data collection period. Note that these are
better than the scan jitter figures would suggest because it is typical data.
With a 1mm sample: max = +0.6 micro m, min = -0.6 micro m, Sigma= 0.2 micro m

With a 30mm sample: max = +9 micro m, min = -9 micro m, Sigma = 3 micro m

rdrast · Dec 1, 2009

The Dynamic range is there on the measurement of the gauge, but best case is still a +/- 1.5 micron error, so no, 1 micron accuracy is not possible.

However, that still doesn't give the analog output accuracies, which should probably be good. Next, is take a look at the spec sheet for your PLC analog input, INCLUDING it's sampling time.

The Input sampling time vs. the gauge's conversion time can also introduce errors, but I feel you will have the greatest error with the PLC analog input, it being a slow, low-cost one.

Analysing analog input from a diameter gauge with 1 micron accuracy !!!!

rajesh_gklm

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