Measurement SG 1/2 bridge (half bridge) 3/5-wire connection

To determine the measuring error:

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
±16 mV/V ⋅ 5V = ±80 mV the internal circuits are designed for the 160 mV of the full bridge measurement.

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 transition resistance values of the terminal contacts affect the measurement. The measuring error can be reduced further through compensation by the user, with active signal connection.

	Validity of property values The resistor of the bridge is positioned parallel to the internal resistor of the terminal and leads to an offset shifting respectively. The Beckhoff factory calibration will be carried out with the half bridge 350 Ω, thus the values specified above are directly valid for the 350 Ω half bridge. By connection of another dimensioned half-bridge is to: perform a balancing (offset correction) by the terminal itself or the control/PLC on application side or the abstract offset error have to be entered into the balancing parameter S0 of the terminal. Example: a 350 Ω half bridge correlates by the compensated effect of the input resistor (2 MΩ) during factory calibration 0.26545 %_FSV (16 mV/V), that corresponds to 20738 digits.

Half bridge calculation:

Measurement SG 1/2 bridge (half bridge) 3/5-wire connection 2:

R_3/4 are the internal switchable input resistors of the terminal. Other configurations (e.g. R_1/4 or R_1/3 variable) of half bridges are not supported

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

Measurement SG 1/2 bridge (half bridge) 3/5-wire connection 3:

N should be chosen based on the mechanical configuration of the variable resistors (Poisson, 2 active uniaxial, …).

Note: specifications apply for 2.5 V SG excitation.

Measurement mode		SG 1/2 bridge
Measuring range, nominal		-16…+16 mV/V [corresponds to ±16000 µε at K=2, N=2]
Measuring range, end value (full scale value)		16 mV/V
Measuring range, technically usable		-17.179…+17.179 mV/V
PDO resolution		24 bit (including sign)
PDO LSB (Extended Range)		2.048 nV/V
PDO LSB (Legacy Range)		1.907.. nV/V
Basic accuracy: Measuring deviation at 23°C, with averaging (²		3-wire connection: ±0.27% typ. (relative to full scale value, q.v. note) 5-wire connection: ±0.09% typ. (relative to full scale value, q.v. note)
Integrated power supply		0.5…5 V adjustable, max. supply/excitation 21 mA (internal electronic overload protection) therefore 120R strain gauge: up to 2.5V 350R strain gauge: up to 5.0V
Temperature coefficient	Tc_Terminal	<75 ppm/K typ. (rel. to full scale value, since production 2016 week 10; refer to serial number) <250 ppm/K typ. (rel. to full scale value, production until 2016 week 09; refer to serial number)
Input impedance ±Input 1 (Internal resistance)		Differential 4.1 MΩ \|\| 11 nF typ.
Input impedance ±Input 1 (Internal resistance)		CommonMode 1 MΩ \|\| 40 nF typ. Methodology: Resistor against -U_V, capacitance against SGND
Input impedance ±Input 2 (Internal resistance)		Differential 5 MΩ \|\| 10 nF typ.
Input impedance ±Input 2 (Internal resistance)		CommonMode 1.25 MΩ \|\| 40 nF typ. Methodology: Resistor against -U_V (+2.5V), capacitance against SGND

²) Dominant part of the basic accuracy is its offset specification (see following tables). The process described in the Offset correction section eliminates this proportion and increases the measurement accuracy considerably.

Measurement mode		SG 1/2 bridge (3 wire)
Offset/Zero Point deviation (at 23°C)	E_Offset	< 2650 ppm_FSV(valid since 2018 week 01; value before 2018 week 01: < 3600 ppm_FSV)
Gain/scale/amplification deviation (at 23°C)	E_Gain	< 290 ppm
Non-linearity over the whole measuring range	E_Lin	< 390 ppm_FSV
Repeatability	E_Rep	< 50 ppm_FSV
Noise (without filtering)⁴	E_{Noise. PtP}	< 950 ppm_FSV		< 7422 [digits]
	E_{Noise. RMS}	< 145 ppm_FSV		< 1133 [digits]
	Max. SNR	> 76.8 dB
	Noisedensity @1kHz	< 32.81
Noise (with 50 Hz FIR filtering)⁴	E_{Noise. PtP}	< 70 ppm_FSV		< 547 [digits]
	E_{Noise. RMS}	< 15 ppm_FSV		< 117 [digits]
	Max. SNR	> 96.5 dB
Common-mode rejection ratio (without filtering)³		DC: < 150 typ.	50 Hz: < 600 typ.		1 kHz: < 10 typ.
Common-mode rejection ratio (with 50 Hz FIR filtering)³		DC: < 100 typ.	50 Hz: < 20 typ.		1 kHz: < 0.1 typ.
Largest short-term deviation during a specified electrical interference test		±0.2%_FSV = ±2000 ppm_FSV typ.

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

⁴) Specifications valid for HW Version ≥ 10, only! Valid specifications until HW Version 10 are as follows:

Measurement mode		SG 1/2 bridge (3 wire), < HW10
Noise (without filtering)	E_{Noise. PtP}	< 1100 ppm_FSV	< 8594 [digits]
	E_{Noise. RMS}	< 160 ppm_FSV	< 1250 [digits]
	Max. SNR	> 75.9 dB
	Noisedensity @1kHz	< 36.2
Noise (with 50 Hz FIR filtering)	E_{Noise. PtP}	< 120 ppm_FSV	< 938 [digits]
	E_{Noise. RMS}	< 19 ppm_FSV	< 148 [digits]
	Max. SNR	> 94.4 dB

Measurement mode		SG 1/2 bridge (5 wire)
Offset/Zero Point deviation (at 23°C)	E_Offset	< 750 ppm_FSV(valid since 2018 week 01; value before 2018 week 01: < 1100 ppm_FSV)
Gain/scale/amplification deviation (at 23°C)	E_Gain	< 290 ppm
Non-linearity over the whole measuring range	E_Lin	< 390 ppm_FSV
Repeatability	E_Rep	< 50 ppm_FSV
Noise (without filtering)⁴	E_{Noise. PtP}	< 1200 ppm_FSV		< 9375 [digits]
	E_{Noise. RMS}	< 175 ppm_FSV		< 1367 [digits]
	Max. SNR	> 75.1 dB
	Noisedensity @1kHz	< 39.6
Noise (with 50 Hz FIR filtering)⁴	E_{Noise. PtP}	< 70 ppm_FSV		< 547 [digits]
	E_{Noise. RMS}	< 14 ppm_FSV		< 109 [digits]
	Max. SNR	> 97.1 dB
Common-mode rejection ratio (without filtering)³		DC: < 150 typ.	50 Hz: < 600 typ.		1 kHz: < 10 typ.
Common-mode rejection ratio (with 50 Hz FIR filtering)³		DC: < 100 typ.	50 Hz: < 20 typ.		1 kHz: < 0.1 typ.
Largest short-term deviation during a specified electrical interference test		±0.2%_FSV = ±2000 ppm_FSV typ.

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

⁴) Specifications valid for HW Version ≥ 10, only! Valid specifications until HW Version 10 are as follows:

Measurement mode		SG 1/2 bridge (5 wire), < HW10
Noise (without filtering)	E_{Noise. PtP}	< 1600 ppm_FSV	< 12500 [digits]
	E_{Noise. RMS}	< 240 ppm_FSV	< 1875 [digits]
	Max. SNR	> 72.4 dB
	Noisedensity @1kHz	< 54.31
Noise (with 50 Hz FIR filtering)	E_{Noise. PtP}	< 96 ppm_FSV	< 750 [digits]
	E_{Noise. RMS}	< 16 ppm_FSV	< 125 [digits]
	Max. SNR	> 95.9 dB

The channel value (PDO) is interpreted directly [mV/V]:

Measurement SG 1/2 bridge (half bridge) 3/5-wire connection 20: — Representation measuring range SG 1/2 bridge