Daytronic Corporation - 5D Series AC Strain Gage Conditioner Module

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AC Strain Gage Conditioner Module

Model 5D78 / 5D78V

The single-channel Models 5D78 and 5D78V are similar to the DC-excited Models 5D70 and 5D70V, respectively, but feature a highly effective phase-sensitive carrier-amplifier design. Three selectable operating frequencies are provided to best match the user's specific transducer.

The 5D78 delivers filtered analog output of ą5 VDC, while the 5D78V produces ą10 VDC.

The 5D78(V)'s advanced analog design directly addresses the problem of measurement inaccuracy in industrial environments of high electromechanical noise. Exceptional signal stability and accuracy over the entire input range are achieved through

	regulated, remotely sensed AC excitation
	precise LINEARITY / SYMMETRY correction and SIGNAL PHASE adjustment via software commands
	high-stability amplification
	configurable low-pass active filtering
	"absolute" and "two-point" software-based calibration
	effective signal isolation and ESD protection

While intended primarily for applications involving transformer-coupling to the transducer bridge (as with conventional rotary-transformer torque sensors), the Model 5D78(V) can also be used when high sensitivity is required or where the electrical environment is especially noisy. Responding only to the modulated carrier frequency, the module rejects extraneous voltages that can cause errors in DC systems, particularly when there is a need to "blow up" a portion of the transducer range.

For both the Model 5D78V and the Model 5D78S (the "S" Option version of the Model 5D78), a 10-pin header for a Phoenix Style screw-terminal connector replaces the Model 5D78's standard DB25 connector for the module's power, configuration, logic, and analog output wiring. Ensuring secure cable connections to individual 5D modules, these versions are intended primarily for single-point or single-mount module applications. Since the logic "enable" line is not provided in this case, both analog outputs are continuously available for both the 5D78V and the 5D78S.

View / download complete
Model 5D78/5D78V Instruction Manual

The 5D78/5D78V Overcomes Errors That Traditionally Plague the Strain-Gage Measurement Process

For steady indication and smooth, dependable control action, the 5D78(V) can provide a true average value of the measured variable, even in the face of substantial dynamic content. As with most 5D Series modules, two high-level, noise-free analog output signals are provided. For the 5D78 (only), one output may be switched on and off by setting the logic state of an "enable" line. For the 5D78V, both outputs are continuously available.

Both models feature

	Powerful low-pass active filtering, independently selectable for each output, for removal of unwanted high-frequency measurement-signal components and the elimination of aliasing errors, if the module's output is subsequently sampled
	High noise rejection, eliminating errors from common-mode pickup and ground-loop coupling, with 1500 VAC isolation between input and output terminals and between I/O and power supply / communications terminals
	High ESD immunity and extensive EMI protection further assure data integrity in harsh industrial environments

Internal "Absolute" Calibration Coupled with High-Accuracy "Two-Point (Deadweight)" Calibration

Because of normal cable loading effects, it is a practical necessity to calibrate any AC TORQUE SENSOR/CABLE/INSTRUMENT system after installation, using a known input standard. The "absolute" calibration provided by the 5D78(V) normally yields a very good first approximation. Conventional "zero and span" calibration may then be easily performedwith the module fully "in place"using the Configurator software supplied with the module. This procedure includes any necessary phase-shift compensation, symmetry trimming, and midscale linearity adjustments.

When calibrated "in place," the 5D78(V) offers excellent stability and interchangeability of units. As long as an initially calibrated 5D78(V)'s setup configuration is exactly transferred to the 5D78(V) that replaces it, no recalibration is usually required to maintain the stated accuracy (see Specifications).

The module also allows fast and easy software-controlled calibration by means of a user-installed shunt resistor.

Model 5D78(V) Specifications [Top

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(Click here for 5D Series General Specifications)

Transducer Types

Conventional 4-arm strain gage bridges, typically transformer-coupled, 120 Ω to 10 kΩ; zero range is 20% of the stated full scale. A screw terminal is provided for user-supplied shunt calibration resistor. The diagrams below show standard 4-wire cabling (for under 20 ft. in length) and 8-wire cabling (for 20 ft. or longer).

Input Ranges (Nominal, Full-Scale) and Accuracy per Excitation Setting

See table, below; selectable when the 5D78(V) is configured. Accuracy is given as % of full-scale overall expected maximum error, following calibration. Note that the highest range selection accommodates actual inputs as high as 4.8 mV/V.

	Excitation
Range (mV/V)	3.27 or 5.00 kHz	10.00 kHz
0.5	0.04	0.06
0.75	0.03	0.04
1	0.02	0.03
1.5	0.02	0.02
2	0.02	0.02
3	0.02	0.02

Excitation

Frequency

3.27, 5.00, or 10.00 kHz; selectable when the 5D78(V) is configured

Voltage

Nominal 3 VAC rms

Accuracy

Dependent on range and excitation; see table, above

NOTE: The full-scale accuracies given in the table refer to the 5D78(V)'s response to substantially undistorted waveform inputs. Any phase shift must be compensated for during calibration. Some gain deviation from transducer data-sheet specifications is normally to be expected as a result of loading the sensor's finite output impedance with intrinsic cable capacitance. The degree of this error will vary with cable type and length.

Amplifier

Normal-Mode Range

15 V rms operating; 240 V rms without damage

Input Impedance (Differential)

Greater than 350 kΩ

Offset

Initial: ą0.05% of full scale
Vs. temperature: ą25 ppm/°C
Vs. time: ą10 ppm/month

Gain Accuracy

ą0.02% of full scale typical, following calibration; see table, above

Gain Stability

Vs. temperature: ą25 ppm/°C;
Vs. time: ą10 ppm/month

Analog Filters

0.2, 2, 20, 200, or 2000 Hz, independently selectable for each output

NOTE: For the Model 5D78(V), the value of the highest allowed corner frequency is dependent on the selected excitation frequency: for an excitation of 10.00 kHz, it is 2000 Hz; for 5.00 kHz, it is 1400 Hz; and for 3.27 kHz, it is 1100 Hz.

Analog Outputs

Filtered ą 0 to 5 VDC (for the Models 5D78 and 5D78S) or ą 0 to 10 VDC (for the Model 5D78V), with linearity maintained for 20% overrange. For the Model 5D78 (only), Output B is switchable via logic "Enable" line.

Logic-Input Functions
(see also General 5D Specs)

Enable, Not Calibrate A, Not Calibrate B
The following diagrams show 5D78 logic input connections for switch closure (no external supply) and active TTL logic, respectively, using the standard module DB25 connector. For the "Enable" function, see 5D Analog Outputs and the description of the MODULE IDENTIFICATION (MID) command.

NOTE: For the Models 5D78V and 5D78S, the Enable function is not provided, and both analog outputs are continuously available.

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