2x 100:1 probes used as differential probes or a REAL differential probe? - Page 1
Forum section: electronics / testgear

author: mcinque
author_rank: Unknown
timestamp: August 02, 2014, 11:32:21 am
content: I'm going to buy something to make "safe"mainsmeasurements with my DSO.Should I:grab 2x 100:1 probes and use them differential probes setting math A-B on the DSO, spending about € 60 orget a testec 100:1 differential probe spending much, much more (about € 365)?I mean: both brings the same results, can you describe some advantages of the REAL differential probes that justify € 305 difference (except saving one DSO input)?

author: omgfire
author_rank: Regular Contributor
timestamp: August 02, 2014, 11:45:33 am
content: CMRR

author: mij59
author_rank: Frequent Contributor
timestamp: August 02, 2014, 11:55:43 am
content: Try this onehttp://www.batronix.com/php/index.php

author: mcinque
author_rank: Unknown
timestamp: August 02, 2014, 12:40:12 pm
content: Quote from: omgfire on August 02, 2014, 11:45:33 amthanks.Quote from: mij59 on August 02, 2014, 11:55:43 amThank you, but AFAIK that is for use onto a DMM as it cannot be compensated (and of course it's not practical to use inside an apparatus).

author: mij59
author_rank: Frequent Contributor
timestamp: August 02, 2014, 01:03:50 pm
content: Quote from: mcinque on August 02, 2014, 12:40:12 pmNo, the Testec TT-SI-9001 is a high voltage differential probe for oscilloscopes.

author: mcinque
author_rank: Unknown
timestamp: August 02, 2014, 01:15:10 pm
content: oh sorry, you're right, the link bring me to the cart where I have one testec TT-HVP-40 high voltage probe!However the TT-SI-9001 is not much far from the one I find here, and If I have some warranty problems it will cost me more to send it back in Germany

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 02, 2014, 03:46:55 pm
content: cmrr, smaller or more compact unit, saving 1 scope channel and avoid turtle slow built in dso math function (i mean like my rigol ds1052e). pintek can cost half your listed price testec.

author: David Hess
author_rank: Super Contributor
timestamp: August 02, 2014, 04:38:23 pm
content: The variable gain function of the oscilloscope can be used to trim the DC common mode rejection of the probes which usually contributes the largest error. If necessary, the AC common mode rejection can be slightly adjusted with the probe compensation.The dedicated differential probe should have a much higher common mode input voltage range for a given gain. When using the oscilloscope in add and invert mode, the maximum sensitivity is limited by the common mode voltage and not the differential voltage. Older differential probes tend to be better in this regard than newer ones or at least newer cheap ones. A 7A13 for instance can operate with a sensitivity of 100mV/div over a common mode range of +/- 1000 volts with x10 probes but an oscilloscope alone will be like 500 times worse. I suspect cheap probes leave this specification out because it makes them look bad.I cannot really comment about the Rigols being slow in add and invert mode because none of my old DSOs slow down when operating like that.If you are making 120 or 240 VAC differential measurements, I would first pick up a pair of inexpensive x10 or x100 probes and see how well they work before buying the more expensive differential probe. You probably should have the normal oscilloscope probes anyway and if they are good enough, you will have saved some money.

author: mcinque
author_rank: Unknown
timestamp: August 02, 2014, 05:44:39 pm
content: Thank you David for the detailed explaination and advice.