Calibration is the process of applying known inputs (such as loads or forces or weights) to a sensor and measuring the output parameter such as voltage or current in response to the applied known inputs. A calibration curve - linear, quadratic, cubic or other function - can be fitted to the obtained data and the resulting equation used to infer applied forces from the output voltage.

Sensors can change their behavior due to repeated use, misuse, abuse or simply with the passage of time.

• To make sure it is working accurately within its specifications
• To meet ISO or other QA/QC requirements
• To make sure the accuracy is in line with international references outside your facility
• To avoid injury, errors or mistakes creeping into your products if sensor is reporting wrong results

We recommend recalibration of your sensors, at least once a year if you use it moderately. If the sensor is put to heavy use then you might want to recalibrate it more frequently on a daily, weekly or monthly basis.  If you suspect that the sensors are not behaving as expected then we recommend that you check the results carefully and send it in for inspection and recalibration immediately.

Loadstar Sensors uses state of the art equipment traceable to NIST standards to perform calibrations. We calibrate each and every sensor before it leaves the building. Our internal standards are much more stingent compared to ISO or other standards. We are not an ISO certified test lab but use NIST traceable equipment, references and dead weights as needed to perform all calibration services. 

For Load Cells we use one of the three pieces of equipment as show below.

Calibrations can either be Digital Calibrations or Analog Calibrations. We calibrate integrated load cells like the iLoad, iLoad TR or iLoad Pro directly using the raw digital output from the sensors. For most resistive load cells mated to DI-100, DI-400 or DI-1000 with USB or Wireless Output, we perfroma a digital calibration that outputs the calibrated values directly in Lbs or Kgs. For most resistive load cells mated to an AI-1000 or AI-1000CV, we perform an analog output that provides a best fit linear curve of Force vs. Voltage.

We apply known values to the sensor and read the resulting output signal. For example in the case of load cells, we place known dead weights (up to 100 lb capacities) or apply reference force using a test frame up to 100K lb.

 

We collect data at at least 5 points for one way calibration and for 9 points for two way calibrations at different load levels (as % of full scale loads).

Apply known loads and read the raw digital values from the Digital Load Cell Interface

A polynomial best fit curve is calculated which yields coefficients A, B, C and D for a cubic curve.  These coefficients are burned into the sensor itself or into the interface device to which the sensor is mated. The applied load is computed during use as follows:

A calibration certificate lists details about the sensor, the equipment used, applied and measured loads with the percentage errors a fraction of the full scale capacity or range of the sensor. A calibration certificate with each of our shipped sensors.

You can view a Sample Digital Calibration Certificate here.

When a customer requests an analog calibration we apply loads and measure the resulting voltage or current output.
At each load position, we read the voltage in the 0.5 to 4.5 V DC range.

A linear curve with Force as the calculated parameter and voltage as the varying parameter is calculated. The equation looks like:

Force = A * Voltage + B

We provide this calibration equation to the customer who can then use it to compute the appleid force in their own application.

You can view a Sample Analog Calibration Sheet here.

The load cells are calibrated under ideal lab conditions in our facility in California. Calibrated values can differ due to a variety of factors such including variations in gravitational fields at different locations, altidtude, environmental conditions such as temperature and humidity, vibration in contacting surfaces etc.

For best results, users should calibrate the sensor in place after mounting it into their particular setup. We suggest that you ask a professional calibration shop to come to your facility and provide calibration service at your location for best results.

• Send us the serial number of the units you want to send in
• Let us know how urgently you need the recalibrated load cells back
• We will send you a formal quote

• If quoted price is accepted, we will convert estimate into an invoice
• Make a payment with credit card or send us a PO 

• Carefully pack and ship the items needed to complete the calibration 
• Include the Invoice # on the box or inside the box 
• Send us the tracking number for the shipment

• If sensor is in good workign condition we will recalibrate
  If sensor needs repair or replacement we will advise options & cost

• We will process the order in 1-2 weeks after receipt
• We will ship sooner if an expedited processing option is selected

If you have good references or test equipment and can apply known values to the sensor, then you can calibrate it yourself. You need to have LoadVUE Pro, SensorVUE or ControlVUE software, has a recalibration utility that can help you recalibrate using a friendly GUI WIndows application that helps you calibrate, burn and test the sensors after calibration.

The calibration utility allows a user to use one of several methods to recalibrate a load cell. These include: