Here we go over what load cell sensitivity is, how to convert load cell output voltage to pounds, kilograms or newtons and more.

1. Phone Number: 1-800-550-0280
Contact Email: contact@tacunasystems.com
Website: https://tacunasystems.com/
Load Cell FAQ
What is load cell sensitivity?
Typical unamplified analog load cells have a sensitivity rating with a unit of
mV/V. This rating is specified on a load cell data sheet often in the 1mV/V –
3mV/V range.
Most quality load cells will come with a factory calibration sheet which
specifies the actual sensitivity rating for each individual load cell produced.
This sensitivity value can be used to convert the load cell’s output to scien-
tific units of weight or force.
How to convert load cell output volt-
age to pounds or kilograms or new-
tons
As mentioned above, each load cell should come with a calibration certifi-
cate denoting the sensitivity for each individual cell. This value can be used
to convert the load cell’s output signal to usable units of weight or force. To
calculate the raw output voltage of the cell relative to the full capacity of the
cell, use the following equation:
where
In other words, the above result will be the voltage output from the cell

2. when fully loaded relative to the full rated capacity.
Typically, load cells are used with amplifiers to transform the small output
voltage to a easily measurable voltage (while conditioning the signal with
filters, etc.). If we add an amplifier to the mix, we have:
where
If we were to convert this output voltage to force or weight, we would use
the ratio of the actual output voltage to the maximum output voltage which
is equal to the ratio of the actual load to the maximum rated load:
or
Rearranging, we can solve for L:
where
Note: Load will be in the
same units as the rated capacity.
If the load cell is not factory calibrated, it must be field calibrated to deter-
mine the sensitivity. To do so, record the no-load output value, then load
the cell with a known load and record the output. Subtract the zero output
voltage and use the resulting voltage as the calibration factor:
where

3. Note: The units for the known load and total rated
capacity should match and thus cancel out.
Does load cell excitation voltage mat-
ter?
Load cells require an excitation voltage to produce an output signal. This is
directly related to the fundamental workings of the internal Wheatstone
bridge. In sort, a higher excitation voltage will produce a higher output volt-
age swing when a load is applied to the cell. So, bigger is better, right?
Yes, to a degree. Larger signals are easier to measure and digitize. Addi-
tionally, assuming the noise is constant, the ratio of signal to noise (SNR)
increases. This is also good from a data quality standpoint.
However, high excitation voltage has drawbacks. Higher voltages through
the resistive strain gauges (which comprise the Wheatstone bridge) will
cause more current to flow and heat the strain gauges.
The cell body acts as a heat sink to keep the gauges cool. If the maximum
rated excitation voltage is exceeded, the heating will cause signal perturba-
tion or gauge failure.
Additionally, in battery operated devices, high excitation voltage (and thus,
current) will cause the battery to be depleted much faster than lower excita-
tion circuits.
Load cell excitation vales are often listed as recommend and maximum ex-
citation voltage. As long as your excitation voltage is not higher than the
maximum, you will be fine.
The recommended value from the cell manufacturer is a good rule of thumb
but there is no harm in a lower excitation voltage. eg. 5v is a very common
(modern) excitation voltage.
Modern instrumentation amplifiers are much better than old designs and do
not suffer from the lower excitation voltage. It is perfectly fine to use a 5V
excitation amplifier with a 10V (recommended) excitation load cell. Just not
the other way round.

4. Finally, be sure your amplifier or other signal conditioning electronics can
handle the common mode voltage produced by the cell’s output relative to
the excitation voltage. This value is 50% of the excitation voltage. eg. 10V
excitation produces a 5V common mode voltage.
Most commonly, amplifiers will provide the excitation voltage to the cell.
When this is the case, you should never provide your own excitation volt-
age. Or at the very least never exceed the excitation voltage provided by
the amplifier.
Phone Number: 1-800-550-0280
Contact Email: contact@tacunasystems.com
Website: https://tacunasystems.com/