Question

A pressure transducer is designed to measure pressure in the range of 0-10bar. It consists of a strain gauge attached to a diaphragm to measure deflections. The strain gauge has nominal resistance of 120 Ω and forms one arm of the Wheatstone bridge circuit. The other three arms each have a resistance of 120 Ω. The bridge out is measured by an ideal instrument. The maximum permissible gauge current is 30mA.

Calculate the excitation voltage, Vs.
If the sensitivity of the strain gauge is 338mΩ/bar and the maximum bridge excitation voltage is used, calculate the bridge output voltage when measuring a pressure of 10bar.

Answer 1

To calculate the excitation voltage (Vs) for the Wheatstone bridge in the pressure transducer, Ohm's law is used with the given resistance and maximum current, resulting in Vs = 3.6V. Calculating the bridge output voltage at 10 bar requires knowledge of the bridge configuration and sensitivity factors.

Step-by-step explanation:

A pressure transducer with a strain gauge is used to measure pressure changes that are converted into an electrical signal using a Wheatstone bridge. To calculate the excitation voltage (Vs) where the gauge has a nominal resistance of 120 Ω and the maximum permissible gauge current is 30 mA, we use Ohm's law (V = IR). Here, V is the excitation voltage, I is the current, and R is the resistance.

V = I × R
V = 30mA × 120Ω
V = 0.03A × 120Ω = 3.6V

Therefore, the excitation voltage, Vs, required is 3.6V.

For the bridge output voltage at 10 bar, we first need to calculate the change in resistance due to pressure (10 bar × 338 mΩ/bar = 3380 mΩ). This change alters the resistance of the strain gauge, disrupting the balance of the Wheatstone bridge, thus creating an output voltage. The calculation of this voltage would require additional information such as the bridge configuration and sensitivity factors.