I just got this load cell to measure and record force of an impact in Newtons (vendor link, amazon link). The sensor can be directly connected to a display like this one to easily read the weight, but in this case I'd like to output the readings to the arduino and record those values in a computer.
I'm assuming that the sensor doesn't output force but some voltage, so I will need to write a code to convert this value to force. To do this, I'm planning on recording the sensor outputs at different loads to get a conversion factor (or function) that I can use in the code to get Newtons. I'm not sure if my whole plan will work, so here are some questions I hope you can help me with:
Can I connect this load cell directly to an Arduino pin to read the output?
I've seen some applications that use an amplifier, is this component necessary?
I'm aware that the entire process has many steps to just measure impact force, but I can't see any simpler method with this sensor. Any comments?
I apologize by the lack of details about the sensor, I'm still waiting to receive a data sheet/wiring instructions.
Thanks in advance!
PS: I found this portable display that I might be able to use to simplify everything, but I think it's too expensive for this application.
No, the output from the load cell is 1.0mV/V to 2.0mV/V. That means that the actual output, with 5V excitation, is 5mV to 10mV. Way too small a voltage for the Arduino to, directly, measure. You will need an amplifier to amplify the voltage to a level that will work with the Arduino ADC.
Yes, as well as a stable source of the excitation voltage.
To reliably measure impact forces you will need a system with high frequency response and an ADC with fast sample rate. I am not sure that you can do that with an Arduino. My experience with measuring impacts* is with a fast digital oscilloscope, a charge mode piezoelectric sensor and charge amplifier. Probably, minimum, $5000.00 worth of high end test equipment.
[*]G switches for auto air bags and self generated shock of ballistic devices.
Hear is what you want to look at. With your sensor you see a sensitivity specification which looks like this:
Sensitivity:1.0- 2.0±0.05mV/V
Next your sensor has a range:
Capacity (kg) 20 30 50 100 200 300 500 1000 2000 (Capacity kg)
In this example your sensor is a tension/compression load cell. It's a simple strain gauge bridge. The bridge has an excitation voltage. In your case that will be between 5 to 10 volts. The way all of this comes together is looking at the sensitivity which is the mV (milli-Volt) output of your sensor per volt of excitation full scale.
Just for example let's use a 100 kg sensor and apply a 10 volt excitation. If the sensor sensitivity is 2.0 mV/V when the sensor has a full scale load of 100 kg the voltage out will be 20 mV. So 0 to100 kg is 0 to 20 mV.
The problem now becomes the fact that your sensor unamplified voltage is only 20 mV in this example. Really low. Hard to accurately measure. What most people do at this point is rely on an HX711 Load Cell Amplifier. The HX711 module as seen in the link makes for easy amplification of your sensor signal. You will find HX711 modules from a dozen different sellers online.
There are other ways to get where you want to go but the HX711 modules are an easy to incorporate solution.
Next you can consider load cells which have built in amplifiers. Just make sure your choice of load cell affords a response time suitable for your application. Your load cell link pretty much covers all you need to know but I do not see response times.
You also mention:
When we want to collect data (data acquisition) you need a way to extract the data and dump it for example into an Excel spreadsheet or similar.
There is also the issue of the response time of your sensor ? Will is respond quickly enough , what’s it’s mass etc
You might be better off with a raw strain gauge bridge .
As @groundFungus pointed out a load cell is not the appropriate sensor to measure an impact or shock.
Exactly what physical force are you trying to measure?