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| RADIO SHACK/MICRONTA 22-195 Multimeter Calibration help |
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| santiniuk:
Hi folks. I'm after some assistance. I recently found my first multimeter purchased some time ago. Its all working but could do with a calibration. It's got sentimental value. I have found the schematic on http://www.alfredpratt.com/tiki-view_blog_post.php?postId=72 As far as I can see the meter is built around a SMC4301F0A which I cannot find any datasheet for. Looking at the schematic I can see pins 23, 24 and 25 have the references to VRF1 and 2. adjustable presets on here. I have measured the voltages on the pins and stored these. A slight tweak to a preset does change the measured value. I have a precision 5V external reference that was measuring 4.96V and I can tweak this to read 5.00V but I would prefer to know the correct method for calibration. I do have a lot of equipment at work available once I know the procedure. Many thanks. |
| Kryoclasm:
Wow, I don't think I have ever seen that one. It looks like a nice meter. What year did you get it? How much did it cost? |
| RacerX:
I have two of these myself... have always liked them even though from "the shack" It was Radio Shack's "flagship" unit in the late 80s, early 90s. I still use mine even though I have much higher end meters now... solid unit has never given any trouble but I am also curious also about the calibration |
| Fraser:
I bought one of these in 'as new' condition only a couple of years ago. No idea why, I just like it :-// My only complaint is that the digits are really skinny by todays standards :) Thanks for the link to a decent image of the schematic. Very useful. |
| santiniuk:
Well it's good to hear others have this meter too. I must admit It's as good as new condition and I've just realised it's about 25 years old :palm: My parents purchased it when I was a young lad hooked on electronics and even now with a lab full of equipment at work I'm still fond of this meter. It brings back memories walking around the UK version of Radio Shack (TANDY) and wondering what to save up for next.... Ah the memories. I'm surprised so far no details of the SMC4301F0A I.C has turned up. The schematic is straight forward enough to see what to 'turn' to calibrate but I'm presuming some reference levels need to be set to complete the calibration. Not looking too hopeful at the moment on calibration method which is unfortunate. Thanks |
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