Help, who can understand this calibration instruction - Page 1
Forum section: electronics / repair

author: daisizhou
author_rank: Super Contributor
timestamp: February 06, 2022, 12:54:50 am
content: The calibration steps are in the picture, I can't understand the circle inside, I hope you can help me, thank you

author: daisizhou
author_rank: Super Contributor
timestamp: February 06, 2022, 03:51:10 am
content: I measured and found the KdB value, please help me to see if it is correct

author: bdunham7
author_rank: Super Contributor
timestamp: February 06, 2022, 04:34:02 am
content: Your KdB value should be something like 0.1, not 0.28, if I'm understanding this correctly. It's the error between your device and the reference and it looks pretty small to me.The sign matters. However, I see that the discrepancy is not linear at the ends of your scale and that may be a problem.Then your 'CLIN' is the amount of correction you need to apply, with CLIN = 1.0000 meaning no correction. You are calculating and then entering a new gain constant and the equation is just giving you the new gain constant by taking the old one and multiplying it by the deviation.So if KdB = 0.1, then 10^(0.1/20) = 1.01157945, meaning you are going to increase the gain constant by about 1.1%. You'll still have issues at the -16 and +10dBM levels.

author: daisizhou
author_rank: Super Contributor
timestamp: February 07, 2022, 12:13:10 am
content: Yes .clin is the calibration number for this calibration based on the last calibration.The original circuit is AD834 circuithttps://www.eevblog.com/forum/repair/how-to-adjust-the-ad834-circuit/.For example, the data at -13, -14, -15, and -16 are read in TP6, which is 100 times magnification of TP4, and -5, -4, -3, and -2 are in the middle. . . 2, 3, 4, 5 are read from TP5 and are 10x magnification of TP4.Of course, 7, 8, 9, and 10 are directly read by TP4.The note on page 3 is this circuit of minehttps://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjh25W6i-P1AhUC8LsIHTzIBrkQFnoECAYQAQ&url=https%3A%2F%2Fwww.analog.com%2Fmedia%2Fen%2Ftechnical-documentation%2Fapplication-notes%2Fan-212.pdf&usg=AOvVaw0P0mRa4oleZk1UWPSh8pSQI don't know where you have no linearity at -16DBM where should I fix it

author: daisizhou
author_rank: Super Contributor
timestamp: February 07, 2022, 12:26:02 am
content: By the way, one thing I almost forgot is the URE3 peak multimeter in the table I don't have，I read the RMS RMS value of the waveform through the Tektronix digital oscilloscope TDS2012, and get the DBM value by calculation.I only have a fluke 8060A and a 187 multimeter, I know the frequency can't reach 500KHZ, so read the data with a digital oscilloscopePlease let me know if you have a better way, thanks

author: bdunham7
author_rank: Super Contributor
timestamp: February 07, 2022, 01:10:54 am
content: Quote from: daisizhou on February 07, 2022, 12:26:02 amThat won't work very well. The URE3 will be much better than 0.1dB accuracy, everything else you have won't even be close. The instrument you are trying to calibrate is likely much more accurate than anything else you have that you are trying to calibrate it with. This is probably why you are seeing unacceptable levels of nonlinearity.

author: daisizhou
author_rank: Super Contributor
timestamp: February 07, 2022, 01:20:26 am
content: Did you know there are cheap instruments that can be tested?Because there are few URE3 peak multimeters available for hobbyists