Question

5) A spring balance is calibrated in an environment at a temperature of 20°C and has the following deflection/load characteristic.

 It is then used in an environment at a temperature of 30°C and the following deflection/load characteristic is measured.

Determine the zero drift and sensitivity drift per °C change in ambient temperature.

6) The following resistance values of a platinum resistance thermometer were measured at a range of temperatures Determine the measurement sensitivity of the instrument in ohms/°C 

Answer 1

5) From the first table(data at 20°C), we see that for every kg of load increased, there is a deflection increase of 20 mm. Also all the points lie on a single straight line. So our sensitivity in this case = 20 mm/kg
From the second table(data at 30°C), we see that for every kg of load increased, there is a deflection increase of 22 mm and the all the points lie on a straight line here as well. Sensitivity in this case = 22 mm/kg.
In the 2nd table, we see that for no load applied, there is a 5 mm deflection. So our zero drift( bias basically) is 5 mm.

Sensitivity drift = difference in sensitivity values at two different temperatures = 22 - 20 mm/kg = 2 mm/kg.
So our sensitivity drift per °C change in temperature at ambient temperature will be = (2 mm/kg)/10° C =0.2 (mm/kg)/°C.

6) From the table we see that for every 30°C change in temperature, there is a resistance change of 7 ohms. Here as well, if we plot the points, they will lie on a straight line. So our measurement sensitivity in this case = 7 ohms/30°C = 0.233 ohms/°C

Answer 2

A spring is caribirated in an imviron ment