TESA gage amplifier
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  1. #1
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    Default TESA gage amplifier

    Shot in the dark I know : I am looking for a schematics diagram for a TESA gage amplifier/readout , analog, suitable for GT21/22 probes ( if that matters ).
    I have some probes but no amplifier and I was shocked to see how much they cost. I think they're pretty simple inside and I used to be able to see myself around an electronic circuit.

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    Really no need to build your own.

    Recommend you trawl ebay for one. They show up pretty regularly for peanuts.

    eg.
    Mercer 122L Bench Comparator Display Unit | eBay

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    Quote Originally Posted by gregormarwick View Post
    Really no need to build your own.

    Recommend you trawl ebay for one. They show up pretty regularly for peanuts.

    eg.
    Mercer 122L Bench Comparator Display Unit | eBay
    +1 even if inop or not the right match, if you have the skills, waay easier to do a repair or a mod than to roll yer own from scratch.

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    Quote Originally Posted by Monarchist View Post
    +1 even if inop or not the right match, if you have the skills, waay easier to do a repair or a mod than to roll yer own from scratch.
    Sure, you are right. But I have no idea how they work or for which kind of probes. I understand there is more than one kind of probe.

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    Quote Originally Posted by AlexO View Post
    Sure, you are right. But I have no idea how they work or for which kind of probes. I understand there is more than one kind of probe.
    I'd bet that "level shifting" and ranging is the easy part as well. Might expect some linearity correction going on, too. Mapping that can get tedious.

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    Quote Originally Posted by Monarchist View Post
    I'd bet that "level shifting" and ranging is the easy part as well. Might expect some linearity correction going on, too. Mapping that can get tedious.
    Yep, my thoughts exactly. Weird enough after hours of torturing Google, not a single diagram and ! old Tesatronic models seem to have vanished - zero data on old stuff. I suppose I have to lay my hands on one and see what's inside. The blokes at eevblog are pretty helpful.

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    Quote Originally Posted by AlexO View Post
    Yep, my thoughts exactly. Weird enough after hours of torturing Google, not a single diagram and ! old Tesatronic models seem to have vanished - zero data on old stuff. I suppose I have to lay my hands on one and see what's inside. The blokes at eevblog are pretty helpful.
    Well, this was eventually sorted out. There are a couple of specialized ( and available ) IC's which together with a small number of passive components will make a gage amplifier be that half or full bridge. Problem solved !

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    Quote Originally Posted by AlexO View Post
    Well, this was eventually sorted out. There are a couple of specialized ( and available ) IC's which together with a small number of passive components will make a gage amplifier be that half or full bridge. Problem solved !
    Hey Alex,
    Interested in the ICs you found. Something from Analog Devices?

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    Quote Originally Posted by BugRobotics View Post
    Hey Alex,
    Interested in the ICs you found. Something from Analog Devices?
    Yep. AD698.
    Seems there are quite a few others do but this one will do the job. Bit pricey - $30 or so.

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    Cool, thanks. Yea saw the same pricing. Interested in this project!

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    Quote Originally Posted by BugRobotics View Post
    Cool, thanks. Yea saw the same pricing. Interested in this project!
    Keep in touch then. I'm tied up for aprox 2 months but after that I'll get going and try make one. It might not be cheaper than the eBay stuff but at least I know what's inside.

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