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Products => Test Equipment => Topic started by: GrievousAngel on February 19, 2021, 01:12:29 am

Title: DIY Active Differential Probe Set -Based around TI INA826EVM Evaluation Kit
Post by: GrievousAngel on February 19, 2021, 01:12:29 am

A friend mentioned using a TI INA826EVM Instrument-grade Diff Opamp Evaluation Kit as the center of an excellent active diff probe set! So found one at DigiKey I think, costing a little over $30USD. Banana & BNC connections and project box were additional cost if you don't have some laying around.

BTW . . . there a 2nd area on the TI PCB for adding another opamp for buffering to improve CMRR loading of lower impedance signal sources. I haven't added that enhancement yet.

It can run off a single voltage rail or a +/- supply. I used a small external switching power supply (+/- 16VDC, dropping the 48VDC) I had from previous DIY studio-grade audio projects (API-like Series 500 DIY modules offered by CAPI).

Bottom line is the DIY Active Diff Probe really preforms exceptionally, bettering any diff probe I've used previously. These things ain't cheap ($150USD to $1000+USD). It is an easy build. I use it to check out DIY analog modules for use in studio settings. The DIY Diff Probe is used with my RIGOL DM3058e DMM and a PICO 4262 Purpose-built Analog OScope/Spectrum Analyzer. It cancels out most of the induced noise at the 'front door'! Also allows you to 'grab' most any interqual circuit measurement without concern of signal or power ground. My version is designed for low voltage analog circuits only.

If interested, search these items Online. If you have a few questions, I'll try to answer them. It took about 2 hours once all items were on the table.

Later,

GrievousAngel

Title: Re: DIY Active Differential Probe Set -Based around TI INA826EVM Evaluation Kit
Post by: egonotto on February 19, 2021, 09:36:26 pm

Hello,

why you choose a INA826?

best regards
egonotto

Title: Re: DIY Active Differential Probe Set -Based around TI INA826EVM Evaluation Kit
Post by: exe on February 20, 2021, 09:31:30 am

Huh, ina826 datasheet made me itching. It seems on the "Output Offset Voltage Drift (mV/°C)", what they really mean is uV/C, not mV/C. Otherwise it's the worst inamp I've ever seen.

Title: Re: DIY Active Differential Probe Set -Based around TI INA826EVM Evaluation Kit
Post by: ogden on February 20, 2021, 10:20:18 am

Quote from: exe on February 20, 2021, 09:31:30 am

Otherwise it's the worst inamp I've ever seen.

Could be so. You are welcome to offer better inamp.
[edit] Preferably with low cost development board which could be used as diff probe adapter without heavy modifications.

Title: Re: DIY Active Differential Probe Set -Based around TI INA826EVM Evaluation Kit
Post by: egonotto on February 21, 2021, 04:06:24 am

Hello,

perhaps the AD8421 with boards from ebay is a good choice.

Best regards
egonotto

Title: Re: DIY Active Differential Probe Set -Based around TI INA826EVM Evaluation Kit
Post by: SilverSolder on February 22, 2021, 03:13:34 pm

Have you got a picture?