[UPDATE]Strange behavior of HW counter of RIGOL DS1074Z - Page 1
Forum section: electronics / testgear

author: whowe
author_rank: Contributor
timestamp: February 06, 2014, 09:50:07 am
content: I just got my new RIGOL DS1074Z and replaced my old DS1072U.When I was playing with it, I found something strange with the hardware counter.If the DS1074Z is just powered up and I use CH1 to probe the built-in 1KHz calibration signal, the hardware counter reads normal (999.253 Hz, not bad). (See Pic 1).But if I press "AUTO" button for a quick auto-setting, the hardware counter reads with big error (984.928 Hz). No matter how I adjust the vertical or horizontal or even some other settings, it never come back to normal. (See Pic 2).To summarize, before I press "AUTO" button, the counter works; after "AUTO" adjustment, the counter is broken and I have to reboot the DS1072U to make it back to normal.It happens to every channel.Is it normal, is there anything I missed? Please help. I really bothers me and confuses me.

author: peter.mitchell
author_rank: Super Contributor
timestamp: February 06, 2014, 10:04:42 am
content: Have you tried it with a different signal source?Just incase the counter still works fine, but it's the built in cal signal that changes?

author: whowe
author_rank: Contributor
timestamp: February 06, 2014, 10:10:30 am
content: Quote from: peter.mitchell on February 06, 2014, 10:04:42 amHi Peter, thank you for your quick reply.I tried different source, different trigger level and some other settings. Those didn't work.I also used my Fluke 189 multimeter to measure the frequency of the calibration signal, it was always a perfect 1.0000 kHz.

author: WVL_KsZeN
author_rank: Regular Contributor
timestamp: February 06, 2014, 11:04:37 am
content: What happens when you change the # of samples? I noticed something similar on D2072. Your screenshots don't seem to work, so I can't read the # of samples that are taken.

author: whowe
author_rank: Contributor
timestamp: February 06, 2014, 11:39:33 am
content: Quote from: WVL_KsZeN on February 06, 2014, 11:04:37 amIn both screenshots (good one and bad one), are 1GSa/s, 6.0Mpts. I changed it to some different numbers and didn't help.

author: electronics man
author_rank: Frequent Contributor
timestamp: February 06, 2014, 11:50:13 am
content: That's strange the software counter seems to work

author: fed0r
author_rank: Newbie
timestamp: February 06, 2014, 09:38:18 pm
content: Here's a video on the software freq counter drawbacks, and apparently HW counter reads steady 1KHz, even after pressing the auto button. Sooo, your scope may be a bit defective, i guess?http://youtu.be/bc49tgS3JpA?t=2m55s

author: whowe
author_rank: Contributor
timestamp: February 07, 2014, 03:17:54 pm
content: Quote from: fed0r on February 06, 2014, 09:38:18 pmWhat's the title of the video? I can't directly access YouTube.I guess I have to wait until the Rigol guys get back from new year holidays.

author: cybermaus
author_rank: Frequent Contributor
timestamp: February 07, 2014, 06:23:53 pm
content: Did you notice the +Width also changes? To 505.0uSIs there a software measurement for the -Width also? Maybe its 511uS?

author: Dave Turner
author_rank: Frequent Contributor
timestamp: February 10, 2014, 11:54:10 am
content: I checked this out on my DS1074Z-S and got the same result.

author: cybermaus
author_rank: Frequent Contributor
timestamp: February 10, 2014, 02:12:10 pm
content: Tested, and mine too. Whats more, I had my DMM connected, and it stayed at 1kHz, so its not the calibration signal that is wrong, but the counter itsself.I also set my -S signal gen to a 1kHz. Same results.Even more weird: if you change the signal source from the hardware counter to CH4 (nothing connected to CH4) it keeps reading the same 984Hz. But if you disconnect CH1 the readout for CH4 also jumps to infinite.Could this be a crosstalk issue? Or a firmware issue (anything can be a firmware issue)Maybe I should do this again with 50Ohm terminators connected to the other channels.Edit: with 50 Ohm terminators, the CH4 nicely shows <15Hz. But then when I removed the 50 Ohms, it kept doing so and I could not recreate that issue that CH4 shows the CH1 frequency. The 984Hz issue however was consistently present. After pressing auto, the hardware counter is wrong.My firmware version is 00.02.00.SP1 DS1074Z-S

author: cidcorp
author_rank: Unknown
timestamp: February 10, 2014, 06:51:25 pm
content: Well I can confirm this does the same thing on the DS1074Z-S I have here on my bench. After first starting up I get a solid 999.256 Hz on the HW Counter, butas soon as I hit The AUTO button, the hardware couter shows 984.930. Software counter seem to work fine no changes.Yes I also confirmed that if you turn the scope on, place CH1 probe on probe calibration terminal, turn on HW counter - shows 999.256 Hz...change Counter to CH2, CH3 or CH4and it shows the same value 999.256 (even with no probles on those channels). Hitting AUTO, drops the value down to 984.930 Hz, and again it stays on the screen whetheryou select CH1, CH2, CH3 or CH4 as the counter source.Seems there is a little firmware issue there. It's getting the signal from somewhere... haven't tried the terminator but I'd expect the same results.The terminator part worries me because that makes me think it is not firmware but more of a signal immunity thing.-EDIT: Oh and before I forget, I did check the full range of the Trigger level just to see if that change would affect the counter, but no differences...

author: cybermaus
author_rank: Frequent Contributor
timestamp: February 10, 2014, 08:04:25 pm
content: I did some more testing, and found a pattern, but also an exception to the patternSo 1000 Hz (1kHz) gives 984.926 Hz?Well, after pressing Auto:100Hz -> 84.2106 Hz1kHz -> 984.926 Hz10kHz -> 9985.00 Hz100kHz -> 99985.0 Hz1MHz -> 999.985 kHz (but alternating between 1000000 and 999985)10MHz-> 10000.0 kHz (so spot on, but due to rounding?)So it seems like he is always missing to count about 15 pulses per secondOr maybe exactly one pulse, but the refresh rate of the counter is 15/s? That would match the fact the lower limit for the counter seems to be 15Hz (the <15Hz message you get with no signal)The 10 MHz may only be correct because the last digits is dropped and rounded.Interestingly, before pressing Auto (so directly after reboot):100Hz -> 100.000 Hz1kHz -> 1000.00 Hz10kHz -> 10000.0 Hz100kHz -> 100000 Hz1MHz -> 999.985 kHz (stillalternating between 1000000 and 999985 ?!10MHz-> 10000.0 kHz

author: matkar
author_rank: Regular Contributor
timestamp: February 11, 2014, 12:43:36 am
content: I have 00.02.01.SP1 software version and I have this issue too. I've tested on channel 1 on different frequencies. It happens if the signal is square or triangle but it doesn't happen with sine wave. The frequency measurement from the menu on the left side seems unaffected. But on the other hand it's less accurate than the counter.

author: whowe
author_rank: Contributor
timestamp: February 11, 2014, 02:11:42 pm
content: Hi, everyone here.RIGOL just game me a call. They conformed this issue and promised a patch or update.

author: whowe
author_rank: Contributor
timestamp: February 18, 2014, 11:48:07 am
content: Quote from: whowe on February 11, 2014, 02:11:42 pmRIGOL just told me that they have released a new official version and will soon send it to me.Does anyone know a way to rollback if I dislike the new version?If anyone is interested, I will post the new firmware after I receive it.