DS2072A ADD/INVERT mode to view differential voltages. How can it be done? - Page 1
Forum section: electronics / testgear

author: sotos
author_rank: Frequent Contributor
timestamp: August 26, 2014, 08:31:09 pm
content: Can someone please show me how can it be done? And guide me through the menu for that. I have got one and I’m lost.Thanks in advance.

author: WesleyK
author_rank: Contributor
timestamp: August 26, 2014, 09:42:11 pm
content: Math menu and select the A-B operation. Or A+B and invert one channel.

author: miguelvp
author_rank: Super Contributor
timestamp: August 27, 2014, 04:35:37 am
content: But very slow!!!!!!Unless someone knows of any tips to make the simple add/invert or subtract a bit faster update wise.

author: Hydrawerk
author_rank: Super Contributor
timestamp: August 27, 2014, 11:28:55 am
content: Maybe try setting a shorter record length?

author: WesleyK
author_rank: Contributor
timestamp: August 27, 2014, 01:03:13 pm
content: Or get yourself a differential probe

author: David Hess
author_rank: Super Contributor
timestamp: August 27, 2014, 03:22:02 pm
content: Quote from: miguelvp on August 27, 2014, 04:35:37 amUse a different oscilloscope then. This is not the first time I have run across complaints that a Rigol DSO is slow in add and invert mode.

author: miguelvp
author_rank: Super Contributor
timestamp: August 27, 2014, 05:00:57 pm
content: I was just more stating it for the OP than asking with the caveat that someone might have a way to speed it up that it's unknown to me.So, yeah, if you need a fast invert add, or subtract at a decent price, use a cheap used analog scope or a differential probe.

author: David Hess
author_rank: Super Contributor
timestamp: August 27, 2014, 05:42:59 pm
content: Quote from: miguelvp on August 27, 2014, 05:00:57 pmOr an inexpensive used DSO. Maybe this problem is common with new cheap DSOs but old DSOs did not suffer from it.The differential probe is a superior solution because add and invert mode suffers from poor common mode range.

author: sotos
author_rank: Frequent Contributor
timestamp: August 27, 2014, 06:24:38 pm
content: Wow thanks for the replies.The cheapest one is this,http://uk.farnell.com/pico-technology/ta041/probe-active-differential-powered/dp/1667343323 USDnearly halve the price of the oscilloscope.

author: WesleyK
author_rank: Contributor
timestamp: August 27, 2014, 07:07:17 pm
content: Testec has one for about €230 at batronix.de. And then you also have a cheap one by Pintek, for about €130 I believe.

author: sotos
author_rank: Frequent Contributor
timestamp: August 27, 2014, 07:27:27 pm
content: Are the cheap ones reliable?

author: David Hess
author_rank: Super Contributor
timestamp: August 27, 2014, 10:40:26 pm
content: Pintek makes some inexpensive ones:http://www.pintek.com.tw/https://www.eevblog.com/forum/testgear/teardown-pintek-dp-25-differentail-probe/My best differential probe is a Tektronix 7A13.

author: MarkL
author_rank: Unknown
timestamp: August 28, 2014, 04:03:48 pm
content: Quote from: David Hess on August 27, 2014, 10:40:26 pmHow do you usually do your probing with the 7A13? Attenuator probes? Dual coax lash-up?

author: David Hess
author_rank: Super Contributor
timestamp: August 28, 2014, 05:02:38 pm
content: Quote from: MarkL on August 28, 2014, 04:03:48 pmI use either x1 or x10 passive probes. Assuming that the loading is not a problem, x1 passive probes tend to work pretty well because for sensitive measurements, the 5 MHz bandwidth limit of the 7A13 would be used anyway.Tektronix made special x10 and x100 probes for the 7A13 and similar differential amplifiers which had DC attenuation adjustments to correct the DC common mode rejection ratio which would otherwise be limited by the attenuation tolerance of the probes.The modern version of the 7A13 was made by Preamble and they were purchased by LeCroy.