FIELD CALIBRATION –
It is also possible to calibrate the DP2000 in the field, which will require the optional calibration kit (Part Number 31030). The instructions for a field calibration are shown here, however please feel free to contact Super Systems at 513-772-0060 if you would like to review the process with us before you begin.
The calibration kit consists of two bottles of saturated salt solution in which each bottle generates a precise relative humidity percentage (R.H. %) value. One bottle is 11.3% R.H., and the other is 75.3% R.H. These two specific calibration points are already pre-programmed into the microprocessor board.
1.0 Open the unit
1.1 Remove the aluminum faceplate of the DP2000 by removing the two allen-head cap screws located on the faceplate. After the screw has been removed, carefully lift the front of the faceplate and remove it. After the faceplate has been removed, it can temporarily be rested in the lid of the open case, to allow access to the components inside. This plate will still be connected to the interior circuit boards, so care should be taken to maintain all existing connections.
2.0 Locate the key components within the unit
2.1 The microprocessor board is located in the right side of the unit. This board contains three very small buttons that are used for calibration. Two are next to one another, and they are marked “75.3%” and “11.3%”, while the other has no label. The unmarked button is the “Calibrate” button. The approximate locations of each button are shown on this diagram:
2.2 The sensor-sampling chamber is located in the back left of the unit. It is the gray rectangular box with brass barb fittings on either side with a plastic gland protruding from the center.
2.3 The sensor probe is positioned in the sensor-sampling chamber. It is held in place by the nut on the plastic gland.
3.0 Remove the sensor probe from the sensor sampling chamber.
3.1 Loosen the plastic gland nut and slowly slide the sensor probe out through the airtight seal.
4.0 Install the sensor probe into the 75.3% salt solution.
4.1 Slip the sensor gland (supplied in the calibration kit) over the sensor probe with the sensor tip protruding from the threaded end of the gland and the sensor wires being flush with the top of the rubber o-ring in the gland. Tighten the gland around the sensor. This does not need to be done with a wrench or other tools, but it does need to be tight enough to prevent ambient air from contaminating the humidity level of the sampling chamber.
4.2 Remove the cap of the 75.3% salt solution and install the sensor gland (with the sensor) into the salt solution. To increase the life of the calibration salts, an effort should be made to minimize the amount of time that the salt solution is exposed to the ambient air.
5.0 Allow the sensor to reach equilibrium with the calibration salt.
5.1 With the power to the unit still turned off, leave the sensor in the calibration salt for a minimum of eighteen (18) hours. It is acceptable to leave the sensor in the salt solution for a longer period of time, even a few days, if desired.
6.0 Begin the 75.3% (Span) calibration process.
6.1 After leaving the sensor in the salt for at least eighteen (18) hours, turn the unit on. The reading on the display is not important at this point.
6.2 Simultaneously press the “75.3%” and “Calibration” buttons on the microprocessor board.
7.0 Verify the 75.3% (Span) calibration by flipping the rightmost toggle switch to “RH.” The display should read 75.3 +/- 0.3.
8.0 Determine the acceptability of the reading.
8.1 The value printed on the chart in Appendix A is a theoretical value, and some variation can be expected. When a calibration is performed at SSI, we certify (in writing) that the unit displays within +/- 1 degree of the theoretical value after it has been calibrated. We would not consider a calibration to be successful unless it is within +/- 1 degree, however in the case of a field calibration, this degree of accuracy may or may not be required. The degree of accuracy that is acceptable is determined by the policy of the person performing the calibration.
NOTE: Keep in mind that the DP2000 only displays whole numbers, and not tenths of a degree. Therefore, a reading of 65°F could be as low as 64.50 or as high as 65.49.
9.0 Allow the sensor to achieve equilibrium at ambient atmosphere.
9.1 After the 75.3% (Span) calibration has been completed, remove the sensor from the calibration salt and replace the cap on the salt.
9.2 Leave the sensor probe in the gland and while the unit is still on, allow it to achieve equilibrium at the ambient atmosphere in the room. This is accomplished by simply leaving the sensor exposed to ambient air for between two and three minutes. You will know when this has been accomplished when the numbers on the display begin to stabilize.
10.0 Install the sensor probe into the 11.3% salt solution.
10.1 Remove the cap of the 11.3% salt solution and install the sensor gland (with the sensor) into the salt solution. To increase the life of the calibration salts, an effort should be made to minimize the amount of time that the salt solution is exposed to the ambient air.
10.2 Turn the unit off.
11.0 Allow the sensor to reach equilibrium with the calibration salt.
11.1 With the power to the unit still turned off, leave the sensor in the calibration salt for a minimum of 24 hours. It is acceptable to leave the sensor in the salt solution for a longer period of time, even a few days, if desired.
12.0 Begin the 11.3% (Zero) calibration process
12.1 After leaving the sensor in the salt for at least twenty-four (24) hours, turn the unit on. The reading on the display is not important at this point.
12.2 Simultaneously press the “11.3%” and “Calibration” buttons on the microprocessor board.
13.0 13.0 Verify the 11.3% (Zero) calibration by flipping the rightmost toggle switch to “RH” The display should read 11.3 +/- 0.3.
14.0 Determine the acceptability of the reading
14.1 The value printed on the chart in Appendix A is a theoretical value, and some variation can be expected. When a calibration is performed at SSI, we certify (in writing) that the unit displays within +/- 1 degree of the theoretical value after it has been calibrated. We would not consider a calibration to be successful unless it is within +/- 1 degree, however in the case of a field calibration, this degree of accuracy may or may not be required. The degree of accuracy that is acceptable is determined by the policy of the person performing the calibration.
NOTE: Keep in mind that the DP2000 only displays whole numbers, and not tenths of a degree. Therefore, a reading of 18°F (-7.8°C) could be as low as 17.50°F (-8.06°C) or as high as 18.49°F (-7.51°C).
15.0 Allow the sensor to achieve equilibrium at ambient atmosphere
15.1 After the 11.3% (Zero) calibration has been completed, remove the sensor from the calibration salt and replace the cap.
15.2 Leave the sensor probe in the gland and while the unit is still on, allow it to achieve equilibrium at the ambient atmosphere in the room. This should take between two and three minutes. You will know when this has been accomplished when the numbers on the display begin to stabilize.
16.0 Re-assemble the unit
16.1 After the calibration process has been completed, remove the sensor probe from the gland and return it to the sensor-sampling chamber, taking care to position it properly.
16.2 Hand-tighten the sensor gland to prevent air from leaking out of the sampling chamber.
16.3 Place the faceplate back into its original position.
16.4 Verify that the system is leak proof by turning on the pump and placing a finger over the sample inlet port. The flow meter on the side of the unit will drop to zero if there are no leaks. If a leak is detected, make sure that all tubing connections are tight, especially the black sensor gland.
16.5 After the unit has passed the leak test, re-fasten the screws into the faceplate and tighten.
17.0 Make sure that all caps are replaced on the calibration salts, and return the DP2000 to service.