Semiconductor Strain Gage Definitions

GAGE FACTOR

The gage factor (G.F.) of strain gage is a dimensionless number defined by the formula

G.F. = (R - Rm)/RE

where

R = nominal unstrained resistance of the gage,

Rm = the measured resistance of the gage under some known strain, E,

and

E = the strain on the gage.

Thermal Coefficient of Gage Factor (TCGF)

The Thermal Coefficient of Gage Factor (TCGF) is due to thermal effects in the silicon matrix of the strain gage inhibiting the flow of electrons. The formula for TCGF is

TCGF = (100 x (GF2 - GF1))/(GF1 x (T2 - T1))

where

GF1 = Gage factor at ambient temperature T1;

GF2 = Gage factor at elevated temperature T2;

T1 = ambient temperature (78 deg F);

and

T2 = elevated temperature.

Thermal Coefficient of Resistance (TCR)

The Thermal Coefficient of Resistance (TCR) is also due to thermal effects in the silicon matrix affecting the flow of electrons. The formula for TCR is given by

TCR = (100 x (R2 - R1))/(R1 x (T2 - T1))

where

R1 = Resistance at ambient temperature T1;

GF2 = Resistance at elevated temperature T2;

T1 = ambient temperature (78 deg F);

and

T2 = elevated temperature.