Looking for suggestions on how best to employ this large microammeter - Page 1
Forum section: electronics / projects

author: intabits
author_rank: Frequent Contributor
timestamp: April 05, 2019, 12:47:25 am
content: I recently picked up this large 50uA microammeter with a blank scale.More details, and rear view at:https://imgur.com/gallery/zoEbn9CIt's quite a special item, so I'm looking for a special project that would justify it's use.I'm leaning very much towards the "jay diddy 5 transistor ESR meter" as this seems perfect for that project, being 50uA and the project needing a custom non-linear scale.But I'd like to hear any suggestions of other uses that this meter could be put to, in the realm of an electronics lab environment, or DIY test equipment .Also, would the large scale be of any specific benefit to the ESR meter project?Or are there other projects where that feature would really shine?TIA...

author: intabits
author_rank: Frequent Contributor
timestamp: April 06, 2019, 11:14:34 am
content: Pressing on...I've now tested this large 5"x7" meter. It is indeed 50uA FSD, with a resistance of 3.9k.Thinking about it some more, that large scale would probably be under utilized just for use in an ESR meter, but then it occurred to me that since a scale has to be created in any case, one could make better use of its large size with multiple scales. It could be part of a more comprehensive capacitance tester, measuring not only ESR, but also leakage and capacitance, with scales for each, and possibly also show leakage test voltage.Just thinking aloud about how that might work:-A rotary switch to select the required test function, and a "test" button to perform it. When not pressed, a relay would connect the DUT to a discharge circuit to ensure it's safe to test, and when pressed, switch over to the testing function. For example, in leakage test mode, while test button not pressed, the meter would show the test voltage (and able to be adjusted by a pot), and then show the leakage current while the test button was active.Any thoughts on that idea?Also, I'm still interested in hearing of any other possible uses for such a large analog microammeter...

author: soldar
author_rank: Super Contributor
timestamp: April 06, 2019, 12:52:56 pm
content: To be honest, I don't know if there is a good use for it from a strictly practical point of view because you can get better digital instruments for lower price.Maybe you could use it to reproduce some older multimeter or similar instrument. Something that would be a faux-antique. A show piece. Something you could use not only for practical purposes but also for show.I have a couple of these classic Italian multimeters. I hardly use them but they will always remain in my collection.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: April 06, 2019, 05:38:26 pm
content: It can be turned into just about anything in terms of voltage or current, using the right shunt. Maybe a line voltage or current meter for your test bench? I don't know if they used a special meter, but RCA made some expanded scale meters that are handy to have. You'd have to research how they did it.

author: intabits
author_rank: Frequent Contributor
timestamp: April 07, 2019, 11:38:45 am
content: Quote from: soldar on April 06, 2019, 12:52:56 pmYes, you're probably right about that. I was starting to think similarly myself.Though I do find the idea of directly viewing the leakage current (or reforming current if that's what's being done) on an analogue meter, rather appealing.I will deliberate further, and probably end up pursuing the setup I outlined previously, because even though not an ideal approach, it would be a fun project.My question was mainly in case I was missing a useful test equipment application for this device that would be absolutely perfect for it, or even one for which such a device would be almost essential, though there probably isn't any.Quote from: Conrad Hoffman on April 06, 2019, 05:38:26 pmI was thinking more of a stadalone portable unit, measuring some esoteric quantity. But any application requiring an expanded scale would be a good fit for this item. Thanks for the suggestion.

author: IDEngineer
author_rank: Super Contributor
timestamp: April 07, 2019, 02:25:07 pm
content: Here's an out-of-the-box idea: I recently saw a video of someone using a meter like that to build an incredibly accurate, high resolution balance scale. He was measuring human eyelashes with it.

author: German_EE
author_rank: Super Contributor
timestamp: April 07, 2019, 04:36:53 pm
content: My vote would be for you to build either a multimeter or an audio millivoltmeter. In the past this would have been ideal for building a VTVM but these days if you want a high impedance voltmeter then you would use a FET

author: floobydust
author_rank: Super Contributor
timestamp: April 09, 2019, 02:09:51 am
content: Kyoritsu used to make panel metersKM-48, KM-66, KM-86, KM-108, KM-118datasheet. The model number is the width in mm. I have vintage KP-110 VU meters from the 1980's.KM-178 is the family of 178mm wide panel meters, quite big. Some have resistors or rectifiers inside, depending on the range and function. You'd have to confirm full-scale.People use them to show server load, or two or three as a time clock, easy to drive from a PWM DAC.

author: intabits
author_rank: Frequent Contributor
timestamp: April 09, 2019, 05:24:18 am
content: Thanks for the link!Quote from: floobydust on April 09, 2019, 02:09:51 amThat seems sensible (except that this meter is 172mm wide?!)QuoteYes, I have. It's 50uA at FSD, with coil resistance of 3900 Ohms.

author: Kalvin
author_rank: Super Contributor
timestamp: April 09, 2019, 02:58:26 pm
content: The display could be used for constructing a nice BS detector: The device would have a microphone and an amplifier driving the ammeter (like a VU-meter), so the needle would move back and forth as someone speaks. Now, the device has also a simple remote-controlled gain adjustment, like IR-remote detector which would increase the amplifier's gain when it detects IR-remote signal. Just hide the IR-remote transmitter somewhere where you can press it while your boss or a person from HR or marketing is speaking ...

author: schmitt trigger
author_rank: Super Contributor
timestamp: April 09, 2019, 03:10:05 pm
content: Kalvin:Love your suggestion. That would certainly be an exceptional office conversational piece!There is a caveat though: You would have to put some sort of overload limiter, otherwise the needle will be bent. At least where I work.Come to think of it, adding a large jumbo red LED to indicate the BS "peaks", like the old analog VU meters used to have, would greatly enhance the BS meter.