Precision amplifier for bridge circuits

AM467

analog microelectronics

February 2011

Analog Microelectronics GmbH

Phone:

+49 (0)6131/91 073 – 0

7/9

An der Fahrt 13, D – 55124 Mainz

Fax:

+49 (0)6131/91 073 – 30

Rev. 1.1

Internet: http://www.analogmicro.de

Email:

info@analogmicro.de

Once these resistors have been mounted the calibration procedure is complete. Depending on the

accuracy of the resistors used an offset value of 0.5 V and a full scale signal of 4.5 V should have

been obtained.

Should the expected final accuracy require it, in an additional second stage (Stage 2) the offset of

measured at P = 0 bar. If at 0 bar the output is too high or too low by a few millivolts, for example,

The offset error which is then obtained if a different resistance is used in place of calculated

has a delta R (in ohms) to the calculated value. The given sensitivity value (mV/ohm) is multiplied

Figure 2: Ceramic sensing element with AM467 and a calibration network

DIMENSIONING

In the combination of ceramic sensing element and AM467 the operating point (the initial value of

the four resistors R1 to R4) was determined for all sensing elements in a specific sensing element

category. In the case of piezoceramic sensors the term "sensing element category" is used to denote

sensing elements with the following characteristics:

Bridge resistance: 11 kOhm ± 20%

Sensitivity: 2.4 ± 1 mV/V

IN+

IN-

AM467

3

2

AMP

VCC

8

OUT

1

GND

4

Vout

GND

C3

C2

R2

R1

R4

R3

Output stage

with short

circuit proofing

C4

C1