Reasonably priced differential probes

[McBryce]

Hi all,
     I'm looking to buy a differential probe without having to spend a fortune. I only need to test up to 240VAC, so I don't need a fat 1000V device. Happy to buy some Chinese device too as long as it is safe for me and my scope.

Any recommendations?

McBryce.

[nctnico]

Look on Ebay for the brand Pintek (Made in Taiwan).

[AndyC_772]

I have one of these:

https://www.picotech.com/accessories/active-oscilloscope-probes/25-mhz-700-v-differential-probe

[McBryce]

Thanks, I'll check those out.

McBryce.

[kripton2035]

I have one of these:

https://www.picotech.com/accessories/active-oscilloscope-probes/25-mhz-700-v-differential-probe

also have one of these, bought used on ebay for some 100€ some 5 years ago
there are from time to time on ebay in europe , just be patient.

[nctnico]

One of the things to decide on is whether to get a mains powered or battery powered diff. probe. Since I hate having test equipment with batteries I choose to buy a mains powered diff. probe.

[Mechatrommer]

I only need to test up to 240VAC, so I don't need a fat 1000V device.

thats what you need, the fat 1000V device. 240Vac is ±330V or 660Vpp (differential), 1000V is the best and safer margin you can get. you seldomly see 660V devices.

[bson]

BitScope also has a sub-$300 differential probe... http://my.bitscope.com/store/?p=view&i=item+7
1.3kVpp, 25MHz, 9V battery or external DC adapter.

[Someone]

I only need to test up to 240VAC, so I don't need a fat 1000V device.

thats what you need, the fat 1000V device. 240Vac is ±330V or 660Vpp (differential), 1000V is the best and safer margin you can get. you seldomly see 660V devices.

The peak withstand voltage for 240V mains in Measurement Category II (CAT II) devices in 61010 is over 2500V peak (I don't recall interpolation being allowed in that table).

Reputable scope manufacturers already include this allowance in their probing solutions. Tek provide clean URLs so we can use them for example:
http://www.tek.com/passive-probe
http://www.tek.com/oscilloscope-probes-and-accessories/differential-probe-high-voltage

The popular P5205A has a measurement range of +/- 1300V (differential or common mode), but carries a rating of 1000V CAT II. It will protect from transient over voltage events, but may not necessarily survive it. The comparable Keysight N2790A specifies a measurement range of +/- 1400V with a rating of 1000V CAT II, but also specifies a non-destructive absolute maximum of +/- 1500V and +/- 1300V RMS CAT II.

Interestingly the P5202A is 300V CAT II with a +/- 640V peak.

[mij59]

I got  the Testec TT-SI-9001 from Batronix http://www.batronix.com/shop/accessory/probes.html

[tautech]

Siglent do 2 models:

DPB3050    50 MHz  800V  US$483
http://www.siglentamerica.com/prodcut-fjxx.aspx?fjid=408&id=-1&tid=1&T=1

DPB4050     50 MHz   6.5 kV US$720
http://www.siglentamerica.com/prodcut-fjxx.aspx?fjid=406&id=-1&tid=1&T=1
This one includes a power adapter.

Pricing may be plus taxes if any.

[McBryce]

I only need to test up to 240VAC, so I don't need a fat 1000V device.

thats what you need, the fat 1000V device. 240Vac is ±330V or 660Vpp (differential), 1000V is the best and safer margin you can get. you seldomly see 660V devices.

Yes, what I meant is that I only need a lower voltage version (I think most start at about 700V), not one of those 10000V RMS big fat isolated ones that cost a fortune.

McBryce.

[electr_peter]

Look on Ebay for the brand Pintek (Made in Taiwan).

Look for Pintek DP-25. Works well, no issues so far.

Forum topics about this model:
https://www.eevblog.com/forum/testgear/%27new-pro%27-differential-probe/
https://www.eevblog.com/forum/testgear/teardown-pintek-dp-25-differentail-probe/

[dadler]

Look on Ebay for the brand Pintek (Made in Taiwan).

I looked into these and found this: http://www.ebay.com/itm/300710178863?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

This looks like a decent product with decent specs, but I wonder if it will match my use case.

I am not all that interested in super high voltages, I mainly want ground isolation. Essentially, want to be able to measure the potential between points in a low-ish voltage circuit (under 30v absolute voltage). Right now I can do the subtract-channels thing, but sometimes the result is noisy and I lose the ability to use XY mode and math functions.

Does anyone know if this differential probe in particular will match my use case, used with, say, a DS2072a or DS1054z? The attenuation and resulting low scope input voltages are what concern me, when used in a relatively low voltage circuit.

[nctnico]

I have the diff. probe from the link above. In the x20 mode the maximum voltage is 35V. This is definitely in the voltage range you are looking for.

[dadler]

I have the diff. probe from the link above. In the x20 mode the maximum voltage is 35V. This is definitely in the voltage range you are looking for.

Ahh I read the specs wrong. Thanks, and thanks for the suggestion. I researched around and found the teardown thread on the forum here and for the price it seems like a good deal.

Just placed an order. 

[slurry]

Still...the absolutely cheapest $0 solution is to use the tips of two probes, just inverting one of the channels, voilá 

[nctnico]

That consumes two channels and has severe limitations. You need to have the channels set to accommodate for the full voltage. If you want to look at a 500mV signal on a 30V offset from ground you'll need to set the scope to at least 5V/div which means the 500mV signal is almost invisible. With a differential probe you can set the scope to 20mV/div or 50mV/div and see the full signal.

edit: type

[slurry]

That consumes two channels and has severe limitations. You need to have the channels set to accomodate for the full voltage. If you want to look at a 500mV signal on a 30V offset from ground you'll need to set the scope to at least 5V/div which means the 500mV signal is almost invisible. With a differential probe you can set the scope to 20mV/div or 50mV/div and see the full signal.

True... but the price is hard to beat 

[DanielS]

Still...the absolutely cheapest $0 solution is to use the tips of two probes, just inverting one of the channels, voilá 

Aside from the sensitivity issues mentioned above, that only works if you have perfect gain and timing match between the two channels.

Using the two probes method to measure voltage across a small current sensing resistor (my main use for differential measurements) is nowhere near as clean as using an instrumentation amplifier or equivalent opamp when possible.

[Mechatrommer]

True... but the price is hard to beat 

but the performance is awful, its better to slap few opamps and volt divider into a active differential probe diy circuit. the diy circuit will be awful but 2dso probes setup is more awful.

[DanielS]

True... but the price is hard to beat 

but the performance is awful, its better to slap few opamps and volt divider into a active differential probe diy circuit. the diy circuit will be awful but 2dso probes setup is more awful.

Instead of slapping a bunch of opamps together, I would try looking at instrumentation amplifiers first: much simpler, far more accurate and possibly cheaper than attempting to match their performance using discrete opamps and precision resistors. You get 80-100dB CMRR with hardly any effort instead of fighting an uphill battle to go beyond 50dB using discretes.

[SArepairman]

have you considered old tektronix p series probes? with attenuator.

[Keylectric]

I have one of these:

https://www.picotech.com/accessories/active-oscilloscope-probes/25-mhz-700-v-differential-probe

Hi, first post for me!

Agilent/Keysight have what seems to be the same product under their brand. A sign of ok quality perhaps if you feel Pico name is not a heavy hitter. Seems to be an ok basic diff probe. Pico pricing is lower.

[Fsck]

I have one of these:

https://www.picotech.com/accessories/active-oscilloscope-probes/25-mhz-700-v-differential-probe

Hi, first post for me!

Agilent/Keysight have what seems to be the same product under their brand. A sign of ok quality perhaps if you feel Pico name is not a heavy hitter. Seems to be an ok basic diff probe. Pico pricing is lower.

the OEM is http://www.sapphire.com.tw/