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How do I connect devices I want to log?

Feb 17, 2015
Christopher Sjokvist wrote
I can not find any instructions on how to connect the device to items I wish to log data on. I am trying to monitor voltages on several wires in a system that is causing trouble. Do I connect a jumper to the voltage source in order to monitor it or do I intercept the signal path on the + and - terminals of the logger?
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17 Answers
Feb 17, 2015
Shawn agent wrote
Christopher,

What instrument are you using (DI-145, DI-710, etc)?

Regards,
DATAQ Instruments Support
Feb 17, 2015
Christopher Sjokvist wrote
DI-155. I want to track voltages that are going to different devices so I can watch for spikes or intermittent faults. How would I connect those devices? I assume I would intercept the signal with the logger. But, I get in trouble when I assume. I'm new to using one of these devices.
Feb 17, 2015
Shawn agent wrote
Christopher,

Analog voltages would connect directly to the DI-155 (across + and -).

Note that the DI-155 has a full scale measurement range of ±50V with overvoltage protection of ±150V (for 1 minute or less).
 
Regards,
DATAQ Instruments Support
Feb 18, 2015
Christopher Sjokvist wrote
Hi,
I am having difficulty understanding this device. I'm a real newbie and apologize for any stupid questions.

I am attempting to read 2 different typed of signals. 3 of them are voltages under 12 v that I need to watch for interference or fluctuations and one of them is a RPM signal from a tach trigger device on a car.

I am not sure how to get a signal to the logger that does not interfere with the operation of the device I am trying to monitor.

For the voltage inputs, do I tap the + voltage wire of my device and attach that to the logger + terminal. Do I need to ground the - terminal of the logger? It seems that I get a cleaner signal if I do that. If I don't, I get an incorrect voltage reading.

For an RPM signal input, do I use a digital input channel? I tried connecting it to the analog channel and got a good reading, but when I added the device that RPM wire goes to, the signal got very noisy and I could not make it better.

I finally found the user manual on your website but it does not answer these questions. Again, sorry if these are dumb questions but I really don't know what I'm doing yet. This logger was suggested to me by the manufacturer of the device I am having issues with and he's on vacation so I am not getting help from him right now.

Thanks,
Chris
Feb 18, 2015
Shawn agent wrote
Christopher,

Yes, you'll want to connect the negative (-) input. The DI-155 includes 4 fixed-differential channels. Each channel measures the potential difference (voltage) between ant two points.

You can connect the RPM signal to the Rate channel (Rate/DI2).

For instruction, see our 'Rate Channel' multimedia presentation at:
http://www.dataq.com/products/di-155/#

Regards,
DATAQ Instruments Support
Feb 18, 2015
Shawn agent wrote
Sorry. You'll find the 'Rate Channel' multimedia presentation at:
http://youtu.be/SAhvB9F5ToI
Feb 19, 2015
Christopher Sjokvist wrote
Hi,
I connected my RPM signal to the digital rate channel #10. I am getting a reading but it looks like a series of steps and not a smooth rate curve following the actual RPM. I've tried different settings and it does not change. Also the scaling needs adjusting. I have an 8 pulse per revolution signal with the engine topping out at 9000 RPM (which means I'll have 72,000 pulses per minute. How do I adjust the graph to compensate for the 8 pulses per revolution?

Thanks,
Chris
Feb 19, 2015
Shawn agent wrote
Christopher,

With the DI-155, you might be better off using one of the analog voltage channels with the Frequency acquisition method (for a smooth rate curve).

See our application note on the Frequency acquisition method at:
http://www.dataq.com/blog/data-acquisition/frequency-and-true-rms-data-acquisition/

You can compensate for the number of pulses per revolution using the Engineering Unit Settings feature (Edit>>Engineering Unit Settings).
Feb 19, 2015
Christopher Sjokvist wrote
Hi,
I get no signal when I do that. I can track the voltage on the wire and can see that as spikes on the screen but when I change it to frequency, it goes away and I can not get anything at all.

If I use a digital input, I can see that stepped signal as I rev the engine but that is not usable for me. I can not get usable data on an analog channel set to log frequency as CPM.

I am getting very frustrated and don't know what to do to try and get this working. I've been at it for 3 days now. I talked to an electronics expert I know and he tried to walk me through setting it up and he could not resolve this. He said I need an oscilloscope to test the signal wire, so I'm getting one hopefully tonight.

Please try and let me know if I'm just missing something or anything at all.

Thanks,
Chris
Feb 20, 2015
Shawn agent wrote
Christopher,

Before choosing the 'Frequency' acquisition method, you'll need to choose a window size and set the trigger level, as outlined in our blog post on Frequency acquisition.

Regards,
DATAQ Instruments Support
Aug 28, 2015
Jeff wrote
When I follow these steps to use the Frequency Acquisition Method (DI-149), both RMS and Frequency are grayed out.

Is this procedure only applicable to the DI-155, or have I missed something in setting up the software? The display shows the voltage, just not in the format I need to record RPM.
Aug 31, 2015
Shawn agent wrote
Jeff,

The Frequency and RMS acquisition methods are not available with the DI-149. The DI-149 does have a Rate channel capable of acquiring frequency up to 10kHz.

See our multimedia tutorial on the subject at:
https://youtu.be/SAhvB9F5ToI

Regards,
Shawn MacDonald
Application Engineer
DATAQ Instruments Inc.
Aug 31, 2015
Jeff wrote
Shawn,

As Christopher pointed out, when using the rate channel as described in the video tutorial I am also seeing the data record as a step function, not a smooth curve, which the data I am recording should be displayed as.

Is there any way to configure the software settings for the DI-149 to record Rate channel data smoothly?

Thanks,
Jeff
Aug 31, 2015
Shawn agent wrote
Jeff,

The Rate channel is only updated every two seconds.

Upon speaking with one of our software engineers, it was brought to my attention that un-checking 'Auto' in the Maximum Sample Rate window (Edit>>Preferences>>Maximum Sample Rate) will allow you to choose the Frequency acquisition method with a DI-149.

Regards,
Shawn MacDonald
Application Engineer
DATAQ instruments Inc.
Sep 05, 2015
Jeff wrote
Thanks, I was able to use the Frequency acquisition settings to record the RPM data with a smooth presentation.
Sep 05, 2015
PAUL CROWE wrote
Jeff, what sample rate did you use?
We run from 1,000 rpm up to 10,000 rpm in just a few seconds (I sell ignition systems) sometimes so I believe from this post that using Rate Channel will not work. If I use frequency acquisition how do I know what to set it at?

Our ignition has a single tach output that can be adjusted from 1-8 pulses per revolution. Most tractors run at 1800 rpm and use our 4 pulse per revolution setting.

How do I connect the tach output if the data logger needs (+) and (-)

Thanks!
Sep 08, 2015
Shawn agent wrote
Paul,

See our multimedia tutorial on the frequency acquisition method at:
https://youtu.be/GESPU2oZfq4

You can connect the negative side of the channel (-) to ground.

Also, I've attached a PDF of our common mode voltage document. Be sure to check for common mode voltage before connecting signals to the DI-149.

Regards,
Shawn MacDonald
Application Engineer
DATAQ Instruments Inc.