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measurement from load cell with NI-6009

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i have a small s type load cell with following specification

capacity = 50 kg

output senstivity = 2 mv/v at F.S

voltage excitation = 5-15 volt

when i connect this with ni6009 and open daq assitant, here i am confused, my question is:

how much input and output voltage should be ranged

i am also confused in RSE and Differential, i dont have basic knowledge about this

i need final data in force unit like kg/m2 or N/mm2

thanks in advance

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@sher786 wrote:

i have a small s type load cell with following specification

capacity = 50 kg

output senstivity = 2 mv/v at F.S

voltage excitation = 5-15 volt

when i connect this with ni6009 and open daq assitant, here i am confused, my question is:

how much input and output voltage should be ranged

i am also confused in RSE and Differential, i dont have basic knowledge about this

i need final data in force unit like kg/m2 or N/mm2

thanks in advance


You need to power the load cell with between 5 and 15 volts. The output will be less than 2mV * excitation, i.e. 50kg will be 10mV if you excite with 5V power supply.

Using a larger excitation voltage will give a larger value to measure (with the minimum 5V, 1kg would only produce a 0.2mV output).

 

Usually you attach an amplifier to the output of a load cell, before trying to measure the voltage produced by the amplifier. Do you have such a device?


GCentral
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@cbutcher wrote:

@sher786 wrote:

i have a small s type load cell with following specification

capacity = 50 kg

output senstivity = 2 mv/v at F.S

voltage excitation = 5-15 volt

when i connect this with ni6009 and open daq assitant, here i am confused, my question is:

how much input and output voltage should be ranged

i am also confused in RSE and Differential, i dont have basic knowledge about this

i need final data in force unit like kg/m2 or N/mm2

thanks in advance


You need to power the load cell with between 5 and 15 volts. The output will be less than 2mV * excitation, i.e. 50kg will be 10mV if you excite with 5V power supply.

Using a larger excitation voltage will give a larger value to measure (with the minimum 5V, 1kg would only produce a 0.2mV output).

 

Usually you attach an amplifier to the output of a load cell, before trying to measure the voltage produced by the amplifier. Do you have such a device?


i dont have any other device, i just have load cell and ni6009 device

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@sher786 wrote:
i dont have any other device, i just have load cell and ni6009 device

The load cell probably has 4 wires. The manufacturer's information will tell you which two are for excitation, and which 2 are for sensing/measuring.

 

You want to connect a power supply to the excitation pair, and the analog inputs to the measurement pair. If you use 2 inputs, you can make a differential measurement.

The measurement types are described in more detail here: Difference Between Differential, RSE, and NRSE Terminal Configurations.

 

Be aware that since you have very small output voltages, without an amplifier it will be difficult (impossible?) to make particularly accurate measurements.

If you need finer resolution than what you can achieve with the NI-6009 alone, you should consider the use of an amplifier.


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@cbutcher wrote:

@sher786 wrote:
i dont have any other device, i just have load cell and ni6009 device

The load cell probably has 4 wires. The manufacturer's information will tell you which two are for excitation, and which 2 are for sensing/measuring.

 

You want to connect a power supply to the excitation pair, and the analog inputs to the measurement pair. If you use 2 inputs, you can make a differential measurement.

The measurement types are described in more detail here: Difference Between Differential, RSE, and NRSE Terminal Configurations.

 

Be aware that since you have very small output voltages, without an amplifier it will be difficult (impossible?) to make particularly accurate measurements.

If you need finer resolution than what you can achieve with the NI-6009 alone, you should consider the use of an amplifier.


thanks for your kind response sir, actually i dont know too much about electonics i am an agriculture engineer, i just want to get force data for my experiment, when i connect the load cell with ni6009 and want to record data, the graph do not show the effect when i give some load, so i want to know if i am using 12 volt for excitation, so what should be the maximum and minmum range of volts, because i calculate the output of load cell it shows mv, so how i give this range in milivolt

i hope you will understand my question

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Message 5 of 17
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i am connecting load cell with ni6009 and want to get readings, but graph shows no changes in reading, iam attaching screenshot of graph, please help

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@sher786 wrote:

when i connect the load cell with ni6009 and want to record data, the graph do not show the effect when i give some load, so i want to know if i am using 12 volt for excitation, so what should be the maximum and minmum range of volts, because i calculate the output of load cell it shows mv, so how i give this range in milivolt


With 12V excitation, the maximum output will be 12V*2mV/V = 24mV @ 50 kg.

The NI-6009 specification sheet shows a table giving accuracy at 25 degrees C (which is hopefully close to the temperature you'll be using it at?). In this table, we can see that the best accuracy is 1.53mV for +-1V input range when making differential measurements.

If you make a single-ended measurement, the accuracy will probably be ~half as good (13 bits instead of 14 bits means 1 less division by 2).

As a result of this, you can probably measure changes of around (1.5 mV / 24mV ) * 50kg = 3.125kg. This is why you would want to use an amplifier - you're only using 24mV of an available 1V in this case.

 

If you instead use +-10V as the input range, your differential accuracy is ~7.73mV. That allows only resolution of about (7.73 / 24) * 50 = 16.1kg.

I'm not sure what accuracy you require, but I'd guess you'd want better than this!

 

This hopefully also explains the problem with your graph (small output voltages only).


GCentral
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@cbutcher wrote:

@sher786 wrote:

when i connect the load cell with ni6009 and want to record data, the graph do not show the effect when i give some load, so i want to know if i am using 12 volt for excitation, so what should be the maximum and minmum range of volts, because i calculate the output of load cell it shows mv, so how i give this range in milivolt


With 12V excitation, the maximum output will be 12V*2mV/V = 24mV @ 50 kg.

The NI-6009 specification sheet shows a table giving accuracy at 25 degrees C (which is hopefully close to the temperature you'll be using it at?). In this table, we can see that the best accuracy is 1.53mV for +-1V input range when making differential measurements.

If you make a single-ended measurement, the accuracy will probably be ~half as good (13 bits instead of 14 bits means 1 less division by 2).

As a result of this, you can probably measure changes of around (1.5 mV / 24mV ) * 50kg = 3.125kg. This is why you would want to use an amplifier - you're only using 24mV of an available 1V in this case.

 

If you instead use +-10V as the input range, your differential accuracy is ~7.73mV. That allows only resolution of about (7.73 / 24) * 50 = 16.1kg.

I'm not sure what accuracy you require, but I'd guess you'd want better than this!

 

This hopefully also explains the problem with your graph (small output voltages only).


thanks sir, i need only data for 10-15 kg load, so should i use amplifier? actually i dont know about signal amplification can you suggest me any signal amplifier which work with ni6009 DAQ

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@sher786 wrote:

thanks sir, i need only data for 10-15 kg load, so should i use amplifier? actually i dont know about signal amplification can you suggest me any signal amplifier which work with ni6009 DAQ


Yes. Use an amplifier. The NI-6009 isn't the thing you really need to target, but instead the load cell. Many companies manufacture load cell amplifiers (I'd start by looking at the company you bought the load cell from) and these may additionally provide a stable power supply to the load cell given a larger input voltage to the amplifier. 

You ideally want to be able to take a 2mV/V input and get a +-10V output or similar (+-5V is probably also fine). I'm not going to make a specific recommendation, just google and choose the one that best fits your budget and also allows a 2mV/V input and a +-10V (or maybe 5V) output.

 

For more generic amplifiers (not specifically aiming for load cell usage) you want to have something where the amplification factor gets you close to that value. Currently you have an output of 24mV, and you'd like 10V, so you need an amplification factor of around 400. If you don't want to get involved with circuit design and specifications, I'd suggest the previous option of finding a load-cell-specific amplifier.


GCentral
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thanks for your response sir, i know i am bothering you so sorry for that, 

i found a signal amplifier here is the link https://www.ato.com/load-cell-transmitter-output-0-5v-4-20ma please tell me is this ok?


@cbutcher wrote:

@sher786 wrote:

thanks sir, i need only data for 10-15 kg load, so should i use amplifier? actually i dont know about signal amplification can you suggest me any signal amplifier which work with ni6009 DAQ


Yes. Use an amplifier. The NI-6009 isn't the thing you really need to target, but instead the load cell. Many companies manufacture load cell amplifiers (I'd start by looking at the company you bought the load cell from) and these may additionally provide a stable power supply to the load cell given a larger input voltage to the amplifier. 

You ideally want to be able to take a 2mV/V input and get a +-10V output or similar (+-5V is probably also fine). I'm not going to make a specific recommendation, just google and choose the one that best fits your budget and also allows a 2mV/V input and a +-10V (or maybe 5V) output.

 

For more generic amplifiers (not specifically aiming for load cell usage) you want to have something where the amplification factor gets you close to that value. Currently you have an output of 24mV, and you'd like 10V, so you need an amplification factor of around 400. If you don't want to get involved with circuit design and specifications, I'd suggest the previous option of finding a load-cell-specific amplifier.


 

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