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DAQ6510 overflow error

DAQ6510 6½-Digit Data Acquisition and Logging Multimeter System
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Cynth77
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DAQ6510 overflow error

Post by Cynth77 » September 7th, 2021, 9:43 pm

Hi, I am working on DAQ6510 for taking temperature measurements using type k thermocouples. I have connected the thermocouples to the 7700 module as given in the user manual. But I am getting overflow error. Can you let me know why I am getting the error and how to correct it. Thanks in Advance.

Andrea C
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Re: DAQ6510 overflow error

Post by Andrea C » September 8th, 2021, 4:31 am

Usually that is because connection issue to the dmm.
On the daq6510 front panel, did you select rear terminals? Must use rear for the 77xx cards to connect to dmm.
Did you close a 77xx channel?

There is user manual and (larger) reference manual.
Section 5 of user manual is dedicated to scanning some temperature channels and walks you through the process.

Last: jumper a 77xx channel hi to LO. A T/C measurement from this shorted channel should be nearly same as the CJC value.

Cynth77
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Country: India

Re: DAQ6510 overflow error

Post by Cynth77 » September 9th, 2021, 4:06 am

Thanks for your response!

Yes, I have selected rear on front panel and have all channels open before giving connections to Device under test, as given in the manual. Getting the same issue with temperature function in front panel measurement too. But I am able to take measurements with other function for eg. DC voltage measurements.

Andrea C
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Re: DAQ6510 overflow error

Post by Andrea C » September 9th, 2021, 4:57 am

You may need to elaborate on what you are doing.

Could be as simple as select a watch channel and select Temperature as the measure function.
Selecting 101 as watch channel will close relay 101 and if properly wired, you will get temperature.
DAQ6510_TC_Watch_Channel.PNG
Reading a thermocouple with DAQ6510
DAQ6510_TC_Watch_Channel.PNG (51.04 KiB) Viewed 185 times
On the swipe screen, you can change the TC type if need be. It defaults to K type.
DAQ6510_TC_type.PNG
T/C sensor settings
DAQ6510_TC_type.PNG (21.96 KiB) Viewed 185 times
If you replace your T/C with a shorting jumper HI to LO, what temperature does it report?
Instead of temperature, use DCV. What voltage does it report?

NOTE: here in the States, for K type we use yellow and red wires. The red is the LO.

Cynth77
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Joined: September 7th, 2021, 9:27 pm
Country: India

Re: DAQ6510 overflow error

Post by Cynth77 » September 13th, 2021, 4:03 am

Found out that there is some problem with the thermocouple. Will use a different one and retry the measurements.

Cynth77
Posts: 5
Joined: September 7th, 2021, 9:27 pm
Country: India

Re: DAQ6510 overflow error

Post by Cynth77 » September 22nd, 2021, 9:50 pm

Hi,
I am getting the same overflow error even with a different thermocouple(US standard- yellow and red). Once the function is set to temperature, it right away starts to show Overflow, with or without interfacing with the thermocouple. Also I have noticed in histogram its showing 100C, for which there is no manual setting, so it can't be changed. Is it because of any issue with the setting? Thanks in advance.
P.S. the current settings are:
buffer size 10000
no of samples 10
scan rate 30s
reference junction -simulated
trigger- continuous

Andrea C
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Re: DAQ6510 overflow error

Post by Andrea C » September 26th, 2021, 7:04 am

You have a connection issue that causes overflow.

Step 1: use front terminals. Put terminal selector switch to front.
Jumper HI to LO with a wire.
Config for T/C. What do you get?
If overflow, what does DCV measure function report?

RichardH
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Re: DAQ6510 overflow error

Post by RichardH » September 28th, 2021, 5:43 am

I'm not sure if this is related, but I recently saw a problem with a voltage channel on a 7706 card. The channel was set to 100mV range and had a 10mV steady signal on it (confirmed with an external meter). I had the channel included in my scan, but after a scan the Reading Table always showed Overflow for that one channel (another channel on the same card was fine). If I measured the problematic channel by manually closing it it worked fine, it was only when the channel was part of a scan.
After a struggle I finally remembered that I had turned off Auto Zero for that channel (to speed up the scan rate). Once I turned Auto Zero back on the channel began to work properly again. My conclusion is "Overflow" can also mean "auto-zero is due."

Andrea C
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Re: DAQ6510 overflow error

Post by Andrea C » September 30th, 2021, 10:02 am

In general, I would not associate overflow with a need for updating auto zero offsets.
Overflow indicates that the measure range in use has been driven into saturation by too high of a signal.

In the case of thermocouple sensor type, open lead detection is on by default. If a open circuit exists, the 100mV range that is used for the T/C will be driven into saturation by the open lead check and overflow value will result.

RichardH: for your situation, what was the appx measured value for the channel prior to the channel that had the 10mV on it? If there is large source resistance and large differences in signal levels in different channels, there can sometimes be extra settling time required.
A quick check on that theory would be to add a shorted HI to LO channel to the scan list right before the 10mV channel. Reading the short will bleed any stored charge off the A/D prior to visiting the 10mV channel.

RichardH
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Re: DAQ6510 overflow error

Post by RichardH » September 30th, 2021, 1:17 pm

Andrea: The channel prior had a 0 to 4 VDC sine wave 0.5 Hz IIRC, coming from an AFG (high resistance? not sure). I repeated the experiment today, in preparation to trying your suggestion, but the Overflow is not happening today (same setup though, I have it saved in a script file).

If it does happen again I will try your suggestion and let you know.

Cynth77
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Joined: September 7th, 2021, 9:27 pm
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Re: DAQ6510 overflow error

Post by Cynth77 » October 10th, 2021, 9:39 pm

Thanks for all your suggestions!

I did all the initial settings and enabled the high limit and set it to 30C and initiated the scan and it displayed measurements without any overflow. Thanks again.

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