Measurement SG 1/1 bridge (full bridge) 4/6-wire connection

Some notes to EPP3504-0023 full bridge measurement:

The nominal/technical measuring range is specified in "mV/V"; the maximum permitted supply voltage is 5 V. The maximum nominal measuring range that can be used for the bridge voltage is therefore ±32 mV/V ⋅ 5 V = ±160 mV; the internal circuits are configured accordingly.

The internal measurement is ratiometric, i.e. the feed voltage and the bridge voltage are not measured absolutely, but as a ratio.

The integrated supply can be used as power supply. An external supply is permitted, as long as 5 V is not exceeded.

The box module has "real" and "compensated" measuring ranges:

The following is the specification given for the 6 wire connection. External line resistances are compensated by the 6 wire connection and the full bridge is detected directly from the measuring channel.
In the 4 wire connection, the box module generally has the same specification, but its view of the connected full bridge is clouded by the unclear and temperature-dependent lead resistances within cables and connectors. In this respect, the overall system "full bridge + leads + measurement channel" will practically not achieve specification values given below.

The lead resistances (cables, connectors, ...) have an effect especially on the gain error, also depending on the temperature. The gain error can be estimated by:

(R+uv (1 + ∆T ⋅ TcCu) + R-uv(1 + ∆T ⋅ TcCu) )/Rnom with TcCu~3930 ppm/K, Rnom

e.g. 350 Ω and R+uv or R-uv lead resistances respectively.

The use of the measurement channel in the 6 wire connection is recommended, especially when significant resistors such as a lightning arrester are put into the line.

By a user-side adjustment with a connected bridge sensor, the measurement uncertainity related to gain and offset error can be significant reduced.

The integrated switcheable shunt resistor can be used to generate a predictable detuning or, in case of deviation, a correction factor.

Note: specifications apply for 5 V SG excitation and symmetric 350R SG.

Note: data are valid from production week 01/ 2019 and

Full bridge calculation:

Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 1:

The strain relationship (µStrain, µε) is as follows:

Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 2:

Measurement mode

StrainGauge/SG 1/1-Bridge 4/6-wire

 

32 mV/V

8 mV/V

 

4 mV/V

2 mV/V

4 mV/V (comp.) 5)

 

2 mV/V (comp.) 5)

Integrated power supply

1…5V adjustable, max. supply/Excitation 21 mA (internal electronic overload protection) therefore
120R SG: up to 2.5 V; 350R SG: up to 5.0 V

Measuring range, nominal

-32 … +32 mV/V

-8 … +8 mV/V

-4 … +4 mV/V

-2 … +2 mV/V

-4 … +4 mV/V

-2 … +2 mV/V

Measuring range, end value (FSV)

32 mV/V

8 mV/V

4 mV/V

2 mV/V

4 mV/V

2 mV/V

Measuring range, technically usable

-34.359 … +34.359 mV/V

-8.590 … +8.590 mV/V

-4.295 … +4.295 mV/V

-2.147 … +2.147 mV/V

-4.295 … +4.295 mV/V

-2.147 … +2.147 mV/V

PDO resolution

24 bit (including sign)

PDO LSB (Extended Range)

0.128 ppm

PDO LSB (Legacy Range)

0.119… ppm

Preliminary specifications:

Measurement mode

StrainGauge/SG 1/1-Bridge 4/6-wire

 

32 mV/V

8 mV/V

 

4 mV/V

2 mV/V

4 mV/V (comp.) 5)

 

2 mV/V (comp.) 5)

Basic accuracy: Measuring deviation at 23°C, with averaging, typ. 2)

without Offset

< ±0.005%FSV
< ±50 ppmFSV
< ±1.6 µV/V

< ±0.012%FSV
< ±120 ppmFSV
< ±0.96 µV/V

< ±0.017%FSV
< ±170 ppmFSV
< ±0.68 µV/V

< ±0.026%FSV
< ±260 ppmFSV
< ±0.52 µV/V

< ±0.024%FSV
< ±240 ppmFSV
< ±0.96 µV/V

< ±0.048%FSV
< ±480 ppmFSV
< ±0.96 µV/V

with Offset

< ±0.015%FSV
< ±150 ppmFSV
< ±4.8 µV/V

< ±0.03%FSV
< ±300 ppmFSV
< ±2.4 µV/V

< ±0.06%FSV
< ±600 ppmFSV
< ±2.4 µV/V

< ±0.12%FSV
< ±1200 ppmFSV
< ±2.4 µV/V

< ±0.06%FSV
< ±600 ppmFSV
< ±2.4 µV/V

< ±0.12%FSV
< ±1200 ppmFSV
< ±2.4 µV/V

Offset/Zero point deviation (at 23°C)

EOffset

140 ppmFSV

280 ppmFSV

560 ppmFSV

1160 ppmFSV

560 ppmFSV

1120 ppmFSV

Gain/scale/amplification deviation (at 23°C)

EGain

40 ppm

100 ppm

140 ppm

220 ppm

200 ppm

400 ppm

Non-linearity over the whole measuring range

ELin

30 ppmFSV

60 ppmFSV

90 ppmFSV

130 ppmFSV

120 ppmFSV

240 ppmFSV

Repeatability

ERep

10 ppmFSV

20 ppmFSV

30 ppmFSV

40 ppmFSV

40 ppmFSV

80 ppmFSV

Common-mode rejection ratio (without filter) 3)

DC

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 3: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 4: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 5: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 6: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 7: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 8: 

50 Hz

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 9: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 10: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 11: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 12: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 13: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 14: 

1 kHz

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 15: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 16: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 17: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 18:

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 19: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 20:

Common-mode rejection ratio (with 50 Hz FIR filter) 3)

DC

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 21: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 22: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 23: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 24:

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 25: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 26:

50 Hz

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 27: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 28: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 29: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 30:

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 31: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 32:

1 kHz

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 33: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 34: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 35: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 36:

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 37: 

tbd. Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 38:

Temperature coefficient, typ.

TcGain

2 ppm/K

4 ppm/K

6 ppm/K

10 ppm/K

8 ppm/K

16 ppm/K

TcOffset

2.4 ppmFSV/K
0.08 Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 39:

10 ppmFSV/K
0.08 Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 40:

24 ppmFSV/K
0.1 Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 41:

50 ppmFSV/K
0.1 Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 42:

20 ppmFSV/K
0.08 Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 43:

40 ppmFSV/K
0.08 Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 44:

Largest short-term deviation during a specified electrical interference test

tbd.

tbd.

tbd.

tbd.

tbd.

tbd.

Input impedance ±Input 1

Differential

tbd.

tbd.

tbd.

tbd.

tbd.

tbd.

CommonMode

tbd.

tbd.

tbd.

tbd.

tbd.

tbd.

Input impedance ±Input 2

4-wire

No usage of this input in this mode

Differential

tbd.

tbd.

tbd.

tbd.

tbd.

tbd.

CommonMode

tbd.

tbd.

tbd.

tbd.

tbd.

tbd.

2) In real bridge measurement, an offset adjustment is usually carried out after installation. The given offset specification of the box module is therefore practically irrelevant. Therefore, specification values with and without offset are given here. In practice, the offset component can be eliminated by the functions Features and also Features of the box module or in the controller by a higher-level tare function. The offset deviation of a bridge measurement over time can change, therefore Beckhoff recommends a regular offset adjustment or careful observation of the change.

3) Values related to a common mode interference between SGND and internal ground.

5) The channel measures electrically to 8 mV/V, but displays its measured value scaled to 2 or 4 mV/V. The Compensated function facilitates measurement of low levels even with high offset.

Noise (with/ without filtering):

Measurement mode

StrainGauge/SG 1/1-Bridge 4/6-wire

 

32 mV/V

8 mV/V

4 mV/V

2 mV/V

Noise (without filtering, at 23°C)

ENoise, PtP

85.0 ppmFSV
664 digits
2.72 µV/V

< 300.0 ppmFSV
< 2344 digits
< 2.4 µV/V

< 600.0 ppmFSV
< 4688 digits
< 2.4 µV/V

< 1200.0 ppmFSV
< 9375 digits
< 2.4 µV/V

ENoise, RMS

15.0 ppmFSV
117 digits
0.48 µV/V

< 50.0 ppmFSV
< 391 digits
< 0.4 µV/V

< 100.0 ppmFSV
< 781 digits
< 0.4 µV/V

< 200.0 ppmFSV
< 1563 digits
< 0.4 µV/V

Max. SNR

96.5 dB

> 86.0 dB

> 80.0 dB

> 74.0 dB

Noisedensity@1kHz

6.79 Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 45:

< 5.66 Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 46:

< 5.66 Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 47:

< 5.66 Measurement SG 1/1 bridge (full bridge) 4/6-wire connection 48:

Noise (with 50 Hz FIR filter, at 23°C)

ENoise, PtP

12.0 ppmFSV
94 digits
0.38 µV/V

< 30.0 ppmFSV
< 234 digits
< 0.24 µV/V

< 60.0 ppmFSV
< 469 digits
< 0.24 µV/V

< 120.0 ppmFSV
< 938 digits
< 0.24 µV/V

ENoise, RMS

2.0 ppmFSV
16 digits
0.06 µV/V

< 5.0 ppmFSV
< 39 digits
< 0.04 µV/V

< 10.0 ppmFSV
< 78 digits
< 0.04 µV/V

< 20.0 ppmFSV
< 156 digits
< 0.04 µV/V

Max. SNR

114.0 dB

106.0 dB

> 100.0 dB

> 94.0 dB