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Unlocking’ RS232 output from CyrusTek IC multimeter

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Blogger Craig had a look at CyrusTek datasheets and found on how to get RS323 data from cheap meters

"There is a band of products within the handheld multimeter market which, regardless of the manufacturer, are all based around an IC family from Taiwanese manufacturer CyrusTek. You can see this in Dave Jones’ multimeter teardowns – nearly all the units he opens up have a CyrusTek IC running the show. So in terms of feature sets they are all on a fairly level playing field; the price spread mostly comes from build & component quality and the user interface design.

If you read the datasheet for those ICs – the ES519xx series – you’ll make the interesting observation that they all do RS232 compliant output. So a vast number of multimeters – quite possibly yours - are capable of serial communication, but most manufacturers don’t break it out to the front panel for you"

For the rest please see here. Trough Hackaday

Might be usefull for people who want to use these multimeters as cheap logging devices...

yeah, i did this to my meter 5 years or so ago.

Uses ES51986 chip.

Button to enable RS232 is hidden under the case between the other 3 buttons, when pressed the IC starts spitting out serial data on one of its pins as 0 - 3.3v uart.

On these models without rs232 they use the same internels and just cut off the top of the gray rubber for the rs232 button so a plastic case without this button hole can be used.
You just need to cut out the plastic and you can press the remaining rubber button with any small object.
Then you can wack in a max232 and opto to get the serial data from the IC pin to your serial port.

I would strongly recommend using an isolated interface like an opto-coupler (PC side could probably be powered from the RS-232 signal). If you directly connect it to your computer, the common jack will be grounded through your computer, like an oscilloscope. This could result in some serious sparks and damaged hardware if you connect the common lead to something else (eg. mains).

Also keep in mind that doing something like drilling holes in the case will void any IEC61010 certification, so I wouldn't even consider using modified meters for anything but <50V CAT I unless you consider yourself able to build to IEC61010 specs. The case is an important component in preventing the user from coming into contact with dangerous potentials and containing blown up components, at least in a properly designed DMM.

Apart from safety issues, it's obviously a neat hack.

Use a reed switch to activate the RS-232 and some sort of wireless interface. Then you don't need to modify the case.


--- Quote from: NiHaoMike on November 30, 2010, 10:45:32 pm ---Use a reed switch to activate the RS-232 and some sort of wireless interface. Then you don't need to modify the case.
--- End quote ---
Don't think you'd want to be transmitting from inside your DMM as it will raise the noise level considerably. I did see one who stuck a transistor driving an IR LED onto the serial line, which seems pretty neat.


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