Measurement SG 1/4 bridge (quarter-bridge) 2/3-wire connection
Notes
- Quarter-bridge measurement in 2-wire operation is not recommended in practice. The normal copper supply cables with their own resistance (e.g. ~17 mΩ/m with 1 mm² wire) and their very high temperature sensitivity (~4000 ppm/K, ~0.4%/K) have a considerable effect on the calculation and can only be corrected by continuous offset and gain adjustment. Only 3-wire operation should be used.
- Specifications apply to 5 V excitation.
The specification deteriorates at lower excitation voltage; Beckhoff does not have detailed information on this.
If a lower excitation voltage is desired for reasons of sensor self-heating, the excitation voltage can be temporarily switched on/off for non-continuous measurements (clocked operation). Switching on/off must be done from the controller via ADS access to the CoE 0x80n0:02. - Specifications only apply when using wire end sleeves and for cross-sections of 0.5 mm² or more. For smaller cross-sections, increased transition resistance is to be expected.
- Avoid repeated insertion/extraction of the push-in connectors in quarter-bridge operation since this may increase the transition resistance.
- Integrated supply: 2...5V adjustable, max. supply/excitation 21 mA (internal electronic overload protection).
Note: effectively only half the voltage is present at the quarter-bridge due to the internally switched bridge supplement.
- Data valid from production week 21/2019 and for EPP3504-0023: HW04/ ERP3504-0022: HW06
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.
To calculate the quarter-bridge:

Explanation:
- R1: external quarter-bridge resistor, nominally 120/350/1000 Ω
- R2: internal supplementary resistor, is set to the same value as R1 after the CoE setting "Interface", and is therefore also 120, 350 or 1000 Ω
- R3, R4: high-resistance internal bridge supplementary resistors, therefore, do not significantly load the internal supply
- Rs: switchable shunt resistor
- SW: internal switch for 2/3-wire operation; open: 3-wire operation
The strain relationship (µStrain, µε) is as follows:

For the quarter-bridge, N=1 always applies.
The relationship between UBridge/UExc and ∆R1 is non-linear:

The EPP3504/ ERP3504 devices apply internal linearization so that the output is already linearized
since the internal calculation is based on UExc'.
Measurement mode |
Measuring bridge/StrainGauge SG 1/4-bridge 120 Ω 2/3-wire | |||
---|---|---|---|---|
32 mV/V |
8 mV/V |
4 mV/V (comp.) 5) |
2 mV/V (comp.) 5) | |
Measuring range, nominal |
±32 mV/V [corresponds to ±64,000 µε at K=2] 120 ±15.36 Ω |
±8 mV/V [corresponds to ±16,000 µε at K=2] 120 ±3.84 Ω |
±4 mV/V [corresponds to ±8,000 µε at K=2] 120 ±1.92 Ω |
±2 mV/V [corresponds to ±4,000 µε at K=2] 120 ±0.96 Ω |
Measuring range, end value (FSV) |
32 mV/V |
8 mV/V |
4 mV/V |
2 mV/V |
Measuring range, technically usable |
±34.359... mV/V |
±8.589... mV/V |
±4.294... mV/V |
±2.147... mV/V |
PDO resolution |
24 bit (including sign) | |||
PDO LSB (Extended Range) |
0.128 ppm |
0.128 ppm |
0.128 ppm |
0.128 ppm |
PDO LSB (Legacy Range) |
0.119… ppm |
0.119… ppm |
0.119… ppm |
0.119… ppm |
Preliminary specifications:
Measurement mode |
Measuring bridge/StrainGauge SG 1/4-bridge 120 Ω 2/3-wire | |||||
---|---|---|---|---|---|---|
32 mV/V |
8 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 |
< ±0.052 %FSV
|
< ±0.16 %FSV
|
< ±0.32 %FSV
|
< ±0.64 %FSV
| |
incl. Offset |
< ±0.2 %FSV
|
< ±0.4 %FSV
|
< ±0.8 %FSV
|
< ±1.6 %FSV
| ||
Offset/Zero point deviation (at 23°C) 4) |
EOffset |
< 1920 ppmFSV |
< 7840 ppmFSV |
< 15680 ppmFSV |
< 31360 ppmFSV | |
Gain/scale/amplification deviation (at 23°C) |
EGain |
< 320 ppm |
< 880 ppm |
< 1760 ppm |
< 3520 ppm | |
Non-linearity over the whole measuring range |
ELin |
< 400 ppmFSV |
< 1300 ppmFSV |
< 2600 ppmFSV |
< 5200 ppmFSV | |
Repeatability (at 23°C) |
ERep |
< 50 ppmFSV |
< 200 ppmFSV |
< 400 ppmFSV |
< 800 ppmFSV | |
Common-mode rejection ratio (without filter) 3) |
tbd. |
tbd. |
tbd. |
tbd. | ||
Common-mode rejection ratio (with 50 Hz FIR filter) 3) |
tbd. |
tbd. |
tbd. |
tbd. | ||
Temperature coefficient, typ. |
TcGain |
< 40 ppm/K |
< 96 ppm/K |
< 192 ppm/K |
< 384 ppm/K | |
TcOffset |
< 100 ppmFSV/K |
< 360 ppmFSV/K |
< 720 ppmFSV/K |
< 1440 ppmFSV/K | ||
Largest short-term deviation during a specified electrical interference test |
0.4 %FSV = 4000 ppmFSV typ. |
0.8 %FSV = 8000 ppmFSV typ. |
1.6 %FSV = 16000 ppmFSV typ. |
3.2 %FSV = 32000 ppmFSV typ. | ||
Input impedance ±Input 1 |
Differential |
tbd. |
tbd. |
tbd. |
tbd. | |
Common- |
tbd. |
tbd. |
tbd. |
tbd. | ||
Input impedance ±Input 2 |
3-wire |
| ||||
Differential |
tbd. |
tbd. |
tbd. |
tbd. | ||
Common- |
tbd. |
tbd. |
tbd. |
tbd. |
Noise (with/ without filtering)/ preliminary data:
Measurement mode |
Measuring bridge/StrainGauge SG 1/4-bridge 120 Ω 2/3-wire | ||||
---|---|---|---|---|---|
32 mV/V |
8 mV/V |
4 mV/V (comp.) 5) |
2 mV/V (comp.) 5) | ||
Noise (without filtering, at 23°C) |
ENoise, PtP |
< 285.0 ppmFSV
|
< 1000.0 ppmFSV
|
< 2000.0 ppmFSV
|
< 4000.0 ppmFSV
|
ENoise, RMS |
< 50.0 ppmFSV
|
< 150.0 ppmFSV
|
< 300.0 ppmFSV
|
< 600.0 ppmFSV
| |
Max. SNR |
> 86.0 dB |
> 76.5 dB |
> 70.5 dB |
> 64.4 dB | |
Noisedensity@1kHz |
< 0.02
|
< 0.02
|
< 0.02
|
< 0.02
| |
Noise (with 50 Hz FIR filter, at 23°C) |
ENoise, PtP |
< 20.0 ppmFSV
|
< 60.0 ppmFSV
|
< 120.0 ppmFSV
|
< 240.0 ppmFSV
|
ENoise, RMS |
< 4.0 ppmFSV
|
< 12.0 ppmFSV
|
< 24.0 ppmFSV
|
< 48.0 ppmFSV
| |
Max. SNR |
> 108.0 dB |
> 98.4 dB |
> 92.4 dB |
> 86.4 dB |
Measurement mode |
Measuring bridge/StrainGauge SG 1/4-bridge 350 Ω 2/3-wire | |||
---|---|---|---|---|
32 mV/V |
8 mV/V |
4 mV/V (comp.) 5) |
2 mV/V (comp.) 5) | |
Measuring range, nominal |
±32 mV/V [corresponds to ±64,000 µε at K=2] 350 ±44.8 Ω |
±8 mV/V [corresponds to ±16,000 µε at K=2] 350 ±11.2 Ω |
±4 mV/V [corresponds to ±8,000 µε at K=2] 350 ±5.6 Ω |
±2 mV/V [corresponds to ±4,000 µε at K=2] 350 ±2.8 Ω |
Measuring range, end value (FSV) |
32 mV/V |
8 mV/V |
4 mV/V |
2 mV/V |
Measuring range, technically usable |
±34.359... mV/V |
±8.589... mV/V |
±4.294... mV/V |
±2.147... mV/V |
PDO resolution |
24 bit (including sign) | |||
PDO LSB (Extended Range) |
0.128 ppm |
0.128 ppm |
0.128 ppm |
0.128 ppm |
PDO LSB (Legacy Range) |
0.119… ppm |
0.119… ppm |
0.119… ppm |
0.119… ppm |
Preliminary specifications:
Measurement mode |
Measuring bridge/StrainGauge SG 1/4-bridge 350 Ω 2/3-wire | |||||
---|---|---|---|---|---|---|
32 mV/V |
8 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 |
< ±0.044 %FSV
|
< ±0.16 %FSV
|
< ±0.32 %FSV
|
< ±0.64 %FSV
| |
incl. Offset |
< ±0.2 %FSV
|
< ±0.4 %FSV
|
< ±0.8 %FSV
|
< ±1.6 %FSV
| ||
Offset/Zero point deviation (at 23°C) 4) |
EOffset |
< 1940 ppmFSV |
< 7840 ppmFSV |
< 15680 ppmFSV |
< 31360 ppmFSV | |
Gain/scale/amplification deviation (at 23°C) |
EGain |
< 240 ppm |
< 760 ppm |
< 1520 ppm |
< 3040 ppm | |
Non-linearity over the whole measuring range |
ELin |
< 360 ppmFSV |
< 1500 ppmFSV |
< 3000 ppmFSV |
< 6000 ppmFSV | |
Repeatability (at 23°C) |
ERep |
< 50 ppmFSV |
< 200 ppmFSV |
< 400 ppmFSV |
< 800 ppmFSV | |
Common-mode rejection ratio (without filter) 3) |
tbd. |
tbd. |
tbd. |
tbd. | ||
Common-mode rejection ratio (with 50 Hz FIR filter) 3) |
tbd. |
tbd. |
tbd. |
tbd. | ||
Temperature coefficient, typ. |
TcGain |
< 24 ppm/K |
< 100 ppm/K |
< 200 ppm/K |
< 400 ppm/K | |
TcOffset |
< 60 ppmFSV/K |
< 220 ppmFSV/K |
< 440 ppmFSV/K |
< 880 ppmFSV/K | ||
Largest short-term deviation during a specified electrical interference test |
0.4 %FSV = 4000 ppmFSV typ. |
0.8 %FSV = 8000 ppmFSV typ. |
1.6 %FSV = 16000 ppmFSV typ. |
3.2 %FSV = 32000 ppmFSV typ. | ||
Input impedance ±Input 1 |
Differential |
tbd. |
tbd. |
tbd. |
tbd. | |
CommonMode |
tbd. |
tbd. |
tbd. |
tbd. | ||
Input impedance ±Input 2 |
3-wire |
|
|
|
| |
Differential |
tbd. |
tbd. |
tbd. |
tbd. | ||
CommonMode |
tbd. |
tbd. |
tbd. |
tbd. |
Noise (with/ without filtering)/ preliminary data:
Measurement mode |
Measuring bridge/StrainGauge SG 1/4-bridge 350 Ω 2/3-wire | ||||
---|---|---|---|---|---|
|
32 mV/V |
8 mV/V |
4 mV/V (comp.) 5) |
2 mV/V (comp.) 5) | |
Noise (without filtering, at 23°C) |
ENoise, PtP |
< 290.0 ppmFSV
|
< 1000.0 ppmFSV
|
< 2000.0 ppmFSV
|
< 4000.0 ppmFSV
|
ENoise, RMS |
< 50.0 ppmFSV
|
< 160.0 ppmFSV
|
< 320.0 ppmFSV
|
< 640.0 ppmFSV
| |
Max. SNR |
> 86.0 dB |
> 75.9 dB |
> 69.9 dB |
> 63.9 dB | |
Noisedensity@1kHz |
< 0.02
|
< 0.02
|
< 0.02
|
< 0.02
| |
Noise (with 50 Hz FIR filter, at 23°C) |
ENoise, PtP |
< 15.0 ppmFSV
|
< 50.0 ppmFSV
|
< 100.0 ppmFSV
|
< 200.0 ppmFSV
|
ENoise, RMS |
< 3.0 ppmFSV
|
< 9.0 ppmFSV
|
< 18.0 ppmFSV
|
< 36.0 ppmFSV
| |
Max. SNR |
> 110.5 dB |
> 100.9 dB |
> 94.9 dB |
> 88.9 dB |
Measurement mode |
Measuring bridge/StrainGauge SG 1/4-bridge 1 kΩ 2/3-wire | |||
---|---|---|---|---|
|
32 mV/V |
8 mV/V |
4 mV/V (comp.) 5) |
2 mV/V (comp.) 5) |
Measuring range, nominal |
±32 mV/V [corresponds to ±64,000 µε at K=2] 1000 ±128 Ω |
±8 mV/V [corresponds to ±16,000 µε at K=2] 1000 ±32 Ω |
±4 mV/V [corresponds to ±8,000 µε at K=2] 1000 ±16 Ω |
±2 mV/V [corresponds to ±4,000 µε at K=2] 1000 ±8 Ω |
Measuring range, end value (FSV) |
32 mV/V 128 Ω |
8 mV/V 32 Ω |
4 mV/V 16 Ω |
2 mV/V 8 Ω |
Measuring range, technically usable |
±34.359... mV/V |
±8.589... mV/V |
±4.294... mV/V |
±2.147... mV/V |
PDO resolution |
24 bit (including sign) | |||
PDO LSB (Extended Range) |
0.128 ppm |
0.128 ppm |
0.128 ppm |
0.128 ppm |
PDO LSB (Legacy Range) |
0.119… ppm |
0.119… ppm |
0.119… ppm |
0.119… ppm |
Preliminary specifications:
Measurement mode |
Measuring bridge/StrainGauge SG 1/4-bridge 1 kΩ 2/3-wire | |||||
---|---|---|---|---|---|---|
|
32 mV/V |
8 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 |
< ±0.04 %FSV
|
< ±0.13 %FSV
|
< ±0.26 %FSV
|
< ±0.52 %FSV
| |
incl. Offset |
< ±0.2 %FSV
|
< ±0.4 %FSV
|
< ±0.8 %FSV
|
< ±1.6 %FSV
| ||
Offset/Zero point deviation (at 23°C) 4) |
EOffset |
< 1960 ppmFSV |
< 7880 ppmFSV |
< 15760 ppmFSV |
< 31520 ppmFSV | |
Gain/scale/amplification deviation (at 23°C) |
EGain |
< 210 ppm |
< 610 ppm |
< 1220 ppm |
< 2440 ppm | |
Non-linearity over the whole measuring range |
ELin |
< 330 ppmFSV |
< 1120 ppmFSV |
< 2240 ppmFSV |
< 4480 ppmFSV | |
Repeatability (at 23°C) |
ERep |
< 50 ppmFSV |
< 240 ppmFSV |
< 480 ppmFSV |
< 960 ppmFSV | |
Common-mode rejection ratio (without filter) 3) |
tbd. |
tbd. |
tbd. |
tbd. | ||
Common-mode rejection ratio (with 50 Hz FIR filter) 3) |
tbd. |
tbd. |
tbd. |
tbd. | ||
Temperature coefficient, typ. |
TcGain |
< 26 ppm/K |
< 50 ppm/K |
< 100 ppm/K |
< 200 ppm/K | |
TcOffset |
< 120 ppmFSV/K |
< 460 ppmFSV/K |
< 920 ppmFSV/K |
< 1840 ppmFSV/K | ||
Largest short-term deviation during a specified electrical interference test |
0.4 %FSV = 4000 ppmFSV typ. |
0.8 %FSV = 8000 ppmFSV typ. |
1.6 %FSV = 16000 ppmFSV typ. |
3.2 %FSV = 32000 ppmFSV typ. | ||
Input impedance ±Input 1 |
Differential |
tbd. |
tbd. |
tbd. |
tbd. | |
Common- |
tbd. |
tbd. |
tbd. |
tbd. | ||
Input impedance ±Input 2 |
3-wire |
No usage of this input in this mode | ||||
Differential |
tbd. |
tbd. |
tbd. |
tbd. | ||
Common- |
tbd. |
tbd. |
tbd. |
tbd. |
Noise (with/ without filtering)/ preliminary data:
Measurement mode |
Measuring bridge/StrainGauge SG 1/4-bridge 1 kΩ 2/3-wire | ||||
---|---|---|---|---|---|
|
32 mV/V |
8 mV/V |
4 mV/V (comp.) 5) |
2 mV/V (comp.) 5) | |
Noise (without filtering, at 23°C) |
ENoise, PtP |
< 350.0 ppmFSV
|
< 820.0 ppmFSV
|
< 1640.0 ppmFSV
|
< 3280.0 ppmFSV
|
ENoise, RMS |
< 70.0 ppmFSV
|
< 140.0 ppmFSV
|
< 280.0 ppmFSV
|
< 560.0 ppmFSV
| |
Max. SNR |
> 83.1 dB |
> 77.1 dB |
> 71.1 dB |
> 65.0 dB | |
Noisedensity@1kHz |
< 0.03
|
< 0.02
|
< 0.02
|
< 0.02
| |
Noise (with 50 Hz FIR filter, at 23°C) |
ENoise, PtP |
< 85.0 ppmFSV
|
< 48.0 ppmFSV
|
< 96.0 ppmFSV
|
< 192.0 ppmFSV
|
ENoise, RMS |
< 14.0 ppmFSV
|
< 8.0 ppmFSV
|
< 16.0 ppmFSV
|
< 32.0 ppmFSV
| |
Max. SNR |
> 97.1 dB |
> 101.9 dB |
> 95.9 dB |
> 89.9 dB |
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.
4) The offset specification does not apply to 2-wire operation, since the offset is increased on the device side. Therefore, a system-side offset adjustment is recommended, see Tare- or ZeroOffset function. The final targeting basic acuuracy within the 2-wire operation is mainingly dependent by the quality of this system-side offset adjustment.
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.
Notice | |
Transition resistances of the connection contacts The transition resistance values of the connection contacts affect the measurement. The measuring accuracy can be further increased by a user-side adjustment with the signal connection plugged in. |
The temperature sensitivity of the box module and thus of the measurement setup can be reduced if an external, more temperature-stable supplementary resistor is used for operation of the box module in half-bridge or even full-bridge mode instead of the internal supplementary resistor for quarter-bridge mode.