Countermeasure If Initial Balance (R Balance) Cannot Be Taken

When bonding a strain gage to a curved surface or when using a semiconductor gage providing a wide resistance range, initial balance may not be taken occasionally. As an emergency countermeasure against such the case, there is a parallel resistance method described below.

Insert the following parallel resistance Rp into the bridge:

Rp = R 2 . Rg/ | R – Rg |

where,

Rg: Resistance of strain gage
R: Nominal resistance of bridge

The side of the bridge to which the parallel resistance is inserted is the opposite side of the strain gage if Rg is larger than R, meanwhile the adjacent side if Rg is smaller than R.

In the case of R=120

Resistance Difference from R (+Ω) 0.6 1.2 1.8 2.4 3.0
Rp (kΩ) 24 12 8.2 6.2 4.7

Precaution : When using resistors of E24 system

Parallel Resistance Inserting Side

Precaution : Avoid inserting Rp to the side where the strain gage is connected. Such connection adversely affects the sensitivity