load cells

[Enzo]

If a load cell has a bridge of strain gages with sensibility of 2 mV/V, and
I apply a V=5v, and the range of force is from 0 to100 Kg, is correct to
say that with the max force applied the V difference should be 100 * 5
*2mV/V = 1V ?

 

[Paul Burke]

Enzo wrote:

If a load cell has a bridge of strain gages with sensibility of 2 mV/V, and
I apply a V=5v, and the range of force is from 0 to100 Kg, is correct to
say that with the max force applied the V difference should be 100 * 5
*2mV/V = 1V ?

Nononononono unless it's given as 2mV/V/kg (which it isn't)

The output at maximum load will be 2mV * 5 = 10mV.

Paul Burke

 

[Pooh Bear]

Enzo wrote:

If a load cell has a bridge of strain gages with sensibility of 2 mV/V, and
I apply a V=5v, and the range of force is from 0 to100 Kg, is correct to
say that with the max force applied the V difference should be 100 * 5
*2mV/V = 1V ?

Force is correctly measured in Newtons ! To use the old fashioned way of
talking ... 1 N = 1 kgf ( not 1 kg ) = 1kg*9.81m/s. F = ma. Check the
sensitivity spec.

Other than that, your calculation seems ok

Graham

 

[John Larkin]

On Thu, 18 Aug 2005 13:04:05 +0100, Paul Burke <paul@scazon.com>
wrote:

Enzo wrote:
If a load cell has a bridge of strain gages with sensibility of 2 mV/V, and
I apply a V=5v, and the range of force is from 0 to100 Kg, is correct to
say that with the max force applied the V difference should be 100 * 5
*2mV/V = 1V ?



Nononononono unless it's given as 2mV/V/kg (which it isn't)

The output at maximum load will be 2mV * 5 = 10mV.

Paul Burke

Right. You only get millivolts out of these things.

John

 

[John Fields]

On Thu, 18 Aug 2005 11:41:48 GMT, "Enzo"
<ternavasio@enzoternavasio.it> wrote:

If a load cell has a bridge of strain gages with sensibility of 2 mV/V, and
I apply a V=5v, and the range of force is from 0 to100 Kg, is correct to
say that with the max force applied the V difference should be 100 * 5
*2mV/V = 1V ?

---
No. What the 2mV/V means is that for every volt of excitation, the
bridge will output 2 millivolts with the maximum rated mechanical
load on the load cell. Like this:

k Vin Fin
Vout = -----------
Fmax

where k is the rated sensitivity of the load cell in mV/V
Vin is the excitation voltage
Fin is the force exerted on the load cell
Fmax is the load scale's full-scale force rating


In your case we'll have:

2mV
----- * 5V * 100kgF
1V
Vout = -----------------------
100kgF


which, after the V's and the 100kgF's cancel out leaves you with:

Vout = 2mV * 5 = 10mV


--
John Fields
Professional Circuit Designer