Each DSCA37 non-linearized thermocouple input module provides a single channel of thermocouple input which is filtered, isolated, amplified, and converted to a high-level voltage output. Signal filtering is accomplished with a five-pole filter which provides 85dB of normal-mode rejection at 60Hz and 80dB at 50Hz. An anti-aliasing pole is located on the field side of the isolation barrier, and the other four poles are on the system side. After the initial field-side filtering, the input signal is chopped by a proprietary chopper circuit. Isolation is provided by transformer coupling, again using a proprietary technique to suppress transmission of common mode spikes or surges.
The DSCA37 can interface to eight industry standard thermocouple types: J, K, T, E, R, S, B and N. Each module has cold junction compensation to correct for parasitic thermocouples formed by the thermocouple wire and input screw terminals on the module. Upscale open thermocouple detection is provided by internal circuitry. Downscale indication can be implemented by installing a 47 MOhm, ±20% resistor between screw terminals 6 and 8 on the input terminal block.
Module output is either voltage or current. For current output models a dedicated loop supply is provided at terminal 3 (+OUT) with loop return located at terminal 4 (-OUT). The system-side load may be either floating or grounded.
Special input circuits provide protection against accidental connection of power-line voltages up to 240VAC and against transient events as defined by ANSI/IEEE C37.90.1. Protection circuits are also present on the signal output and power input terminals to guard against transient events and power reversal. Power lines are secured to the module using screw terminals which are in pluggable terminal blocks for ease of system assembly and reconfiguration.
The modules have excellent stability over time and do not require recalibration, however, zero and span settings are adjustable up to ±5% to accommodate situations where fine-tuning is desired. The adjustments are made using potentiometers located under the front panel label and are non-interactive for ease of use.
Frequently Asked Questions
Can Dataforth provide calibration reports for modules I purchased?
Yes we can provide calibration reports for the modules that you purchased.
You can either
a) visit https://www.dataforth.com/TestDataReport.aspx to search for Test Report Datasheets by Serial Number or
b) you can send us a list of model numbers and their serial numbers to firstname.lastname@example.org
Does Dataforth have any DSCA modules that can operate on a 12Vdc power supply?
Dataforth does not have any custom modules that run on 12VDC power. Most DSCA modules require a minimum power supply voltage of 15VDC while some require a minimum of 19VDC. Both are suitable for use with nominal 24VDC power supplies over the full operating temperature range of -40C to +85C. Dataforth offers a line of accessory power supplies, PWR-PS5RxW, which have been qualified for use with the DSCA product line. https://www.dataforth.com/catalog/pdf/PWR-PS5RxW.pdf
Is the calibration of Dataforth modules traceable to NIST standards?
Yes, calibration of Dataforth modules is traceable to NIST standards.
If the input range of my signal conditioner is -1V to +1V and the output range is 0 to 10V, does this mean that it ignores polarity?
A signal conditioner with these I/O ranges does not mean that the module ignores the polarity of your voltage input. The output of voltage input modules are scaled linearly, meaning an input of -1V would correspond to an output of 0V, an input of 0V would correspond to an output of 5V, an input of +1V would correspond to an output of 10V, and so on.
How do I convert an RMS voltage to its corresponding peak voltage?
To convert an RMS voltage to its corresponding peak voltage, you simply take the RMS voltage value and multiply it by the square root of 2, or roughly 1.414.
For example, 1500Vrms corresponds to a peak voltage of 1500 * 1.414 = 2121 Vp
What is the output resolution of the DSCA series?
The DSCA series is completely analog, so the output resolution cannot be expressed in terms of bits as it is not a digital signal. The only thing that would cause any uncertainty/lack of clarity in your output signal would be the output ripple and noise, which is rated at a typical value of 0.025% span RMS as listed in the datasheet.
How does the load resistance of a module affect the noise at the output?
Noise at the output of a module is independent of load resistance.
If a thermocouple is soldered to a lead that has current running through it, how do you avoid affecting the thermocouple signal and subsequent measurement?
The thermocouples must be isolated so current does not come from the circuit under test and run through them. SCM5B, SCM7B, 8B, DSCA, DSCT, MAQ20 all offer the required isolation.
What size wires do the DSCA modules accept?
DSCA module screw terminals are rated to wire gage AWG: 28 – 12.
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