How to Calibrate an SC-200 LVDT Signal Conditioner

In this video, we will demonstrate how to calibrate the SC-200 industrial LVDT signal conditioner from Alliance Sensors Group.

To perform this task, you will need the following:

 -An SC-200 LVDT Signal Conditioner

- An AC LVDT to be calibrated

- An LVDT test fixture with digital micrometer

- A 24V DC power supply

- A DC voltmeter or Digital multimeter

- Small Screwdriver

The SC-200’s factory default settings are adequate for most standard industrial LVDTs and no adjustments are typically required. However, in the event that your LVDT requires different settings from the factory defaults you will need to configure the SC-200 to match to your particular requirements. To perform these adjustments, carefully push in the tabs on both the top and bottom of the signal conditioner’s case with a small screwdriver, then slide the board out from the case to provide access to the DIP switches and jumpers. Consult the label on the case or the SC-200 Manual and its Quick Start Guide instructions to find the correct DIP switch positions and jumper settings for your specific application.

After any internal configurations are complete, begin by connecting the 24-Volt power supply. Connect the positive side of the power supply to terminal 4 of the red J4 terminal plug and the negative side of the power supply to terminal 3.

Next connect the digital voltmeter, which will measure the output from the SC-200. Connect the positive probe of the voltmeter to terminal 4 of the J3 green terminal plug and the negative probe of the voltmeter to terminal 3 of J3.

When connecting the LVDT, attach the primary high of the LVDT to terminal 1 of the J1 black terminal plug and the primary low to terminal 2. Then connect the secondary 2 high of the LVDT to terminal 3 of the J1 black terminal plug and attach the secondary 1 high to terminal 4 of the black plug.

The 2 remaining secondary wires must be connected together and can be attached to terminal 1 of the J2 blue plug for convenience if the leads are long enough. If you are uncertain about the LVDT’s connections, make the secondary connections using the 2 magnetic dots as your guide. If the connections give you the wrong directional sense of output, interchange the 2 primary connections or flip DS2-3 on the SC-200 signal conditioner’s pc board to ON.

For this demonstration we’ll be using an LVDT with a plus and minus 0.50-inch measuring range, which the SC-200 recognizes as a total measuring range of 1.00 inch, along with the SC-200’s default analog output of 0-to-10 VDC, set with DS1-4 turned ON.

Now, with all the connections made and the LVDT positioned into the test fixture we will apply the 24-VDC power to the SC-200. The red Power LED on the face of the unit will illuminate, indicating power is present. The green “P” LED will illuminate as well, indicating that the SC-200 is operating as a stand-alone master. It is important to allow 15 minutes for the SC-200 to fully warm up before proceeding with its calibration.

With the SC-200 fully warmed up, we are ready to place the SC-200 into CAL (calibration) mode. This is accomplished by pressing both the “Full Scale” and “Zero” buttons simultaneously until the red power LED begins to blink, which indicates that the SC-200 is now in calibration mode.

Using the micrometer, adjust the LVDT’s core position until the SC-200’s zero (0) indicator LED glows solid. This is the null point of the LVDT where the core is at the center of its stroke. Now, reset the digital micrometer readout to zero.

Next, using the digital micrometer, move the LVDT’s core inward to minus 0.500 inches. This will take us to the negative end, or 0.00-inch core position, of the LVDT’s stroke, and will be the SC-200’s 0.00 VDC output position. Enter this zero point position into the SC-200 by momentarily holding the “Zero” button down until the positive (+) indicator blinks once. The negative (-) indicator will now glow solid and the positive (+) indicator will begin to blink. This shows that we have successfully set the zero-point position. Do not pay attention to the SC-200’s DC output while performing a calibration.

Now, reset the digital micrometer readout to zero again.

Next, we move the LVDT’s core outward by 1.000 inch. This will take us to the positive end, or 1.00-inch position of the LVDT core’s stroke, and will be the SC-200’s 10.00 VDC Full Scale output position. When that position has been reached, momentarily hold the “Full Scale” button down until both the positive and negative indicators illuminate solid. This indicates that the system calibration has been successfully completed.

Finally, to return the SC-200 to its RUN Mode, press both the “Full Scale” and “Zero” buttons simultaneously until the red Power indicator glows solid. The measuring system is now ready for operation.

We can now observe that the DC voltmeter displays an output voltage of 0.00 VDC from the SC-200 with the LVDT’s core at the 0.00-inch position (not Null) and +10.00 VDC when the LVDT’s core is at the 1.00-inch position.

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SC-200 Series

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