Digital Voltmeter with NI USB-6009

[LawrenceFormula]

I need help creating a digital voltmeter to graph changes in voltage over time in LabVIEW.

I am currently working to measure forces on various suspension components using strain gauges for a club. I am getting good readings using analog inputs; however, I hope also to use digital inputs to record data from more gauges at a time (18 total) since the DAQ I am using only has eight analog inputs. I am using an HX 711 to convert the analog signal from the gauges to a digital signal. I am recording these signals with a NI USB-6009 DAQ. I have messed around for a while and am currently stuck. I believe I need some sort of a loop to output clock signals to the HX 711. Ideally, the program would take continuous samples, but I ran into issues when attempting this (error 200077). 

Any help would be very much appreciated, this is my first time using LabVIEW! I haven't noticed any programs that already exist for this application, I'm sure it would be quite simple for someone who knows what they're doing.

[santo_13 · Accepted solution]

In short, you cannot interface USB-6009 with HX711 as it requires a protocol with tight timing requirements. You can use an Arduino or like to interface with the HX711 bridge amplifier/ADC.

https://forums.ni.com/t5/LabVIEW/Weight-Scale-using-DAQ-USB-6000-and-HX711/td-p/4295820

I recommend looking at a DAQ that supports several gauge readings instead of going through HX711 + digital interface for a more robust system.

If you need a more affordable DAQ, check out LabJack and MCC DAQ

[LVNinja]

Alternatively you could use an arduino connected to the HX71 and read Arduino readings through serial VISA. The arduino is a serial communication, that spits the readings from the loadcell connected to HX71. 

[LawrenceFormula]

Just a quick update, I ended up junking the hx 711's and went with some cheap AD 620 voltage amplifiers instead. Easy to use and plot waveform graphs with; however, they do tend to lose calibration overtime, so I do not recommend this setup. Good proof of concept, but difficult to read accurate changes in voltage from since they don't stay calibrated. Currently working on finding a more accurate, yet still affordable system.

[santo_13]

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@LawrenceFormula wrote:

Just a quick update, I ended up junking the hx 711's and went with some cheap AD 620 voltage amplifiers instead. Easy to use and plot waveform graphs with; however, they do tend to lose calibration overtime, so I do not recommend this setup. Good proof of concept, but difficult to read accurate changes in voltage from since they don't stay calibrated. Currently working on finding a more accurate, yet still affordable system.

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As you realized, if you need a stable, calibrated, professional system, you need shell out more money. I am not justifying the corporates, just the reality that a DIY-like solution is not always professional.