Mar
30
2015
DSC2000 Calibration - Pressure Transducer
A PDF copy of this blog is available. Please find SUP0074 in the support section.
Overview
1) It is recommended that Transducer Calibration is carried out by qualified personnel at a periodic interval defined by the local Standards.
2) The recommended method for Dual Point Calibration is to use a certified Reference Device that is at least as accurate as the resolution required for the Transducer to be calibrated.
3) This Support Document covers dual point calibration in CLISP Studio for Pressure transducers connected to a DSC 2000M for dynamic triaxial testing and a DSC 2000MM for Dynamic simple shear or Dynamic triaxials with dynamic cell pressure control.
4) It is assumed that:
- CLISP Studio is running
- The DSC to which the Transducer is connected has been added in CLISP Studio
- The DSC 2000 is communicating with Clisp Studio
Calibrating a Pressure Transducer
To start the calibration processes open the DSC 2000 Instrument Window in Clisp Studio and select the Analogue Inputs Tab
Important
When calibrating a pressure transducer it is very important that the correct units are used. The transducer units must be set to MPa in Clisp Studio.
To edit the calibration setup it may be required that you press the Edit button and enter the passcode 2603.
Calibration Initial Setup
Now add the zero and FSD. The Zero is normally 0 and the FSD is the maximum pressure that the transducer can read. In most cases this is 1 MPa. This can be found on the Calibration certificate supplied with the transducer.
Lastly make sure Dual Point is selected. Single factor calibrations cannot be used with the DSC 2000. Once this has been completed press the ‘Write’ button (see Figure 4).
There are two ways the calibration can be completed either by using the calibration certificate or using a reference device.
Calibration using the Calibration Certificate
In Clisp Studio open the advanced tab, the first number we need to enter is the Raw Divisions at Full Scale
This number can be calculated from a value that is found on the calibration certificate; the number required is the Rated Pressure Span Output as is highlighted in figure 3.
This number must be put through the following calculation:
So from the example calibration certificate in figure 3 above you would get the following answer:
100.07 / 10000 = 0.010007
So the following would be entered into the raw divisions at full scale. Once this has been entered press the write button.
To complete the Raw divisions at Zero ensure that the transducer is at is zero pressure (usually when released to Atmospheric pressure). Then press the Zero button.
Calibration using Reference Device (APCH)
It is normal to use an APC(H) as a Pressure Reference Device for calibrating a Pore Water Pressure (PWP) Transducer (APC Calibration is covered in SUP0033).
1) Attach the Pore Water Pressure transducer to one of the Pore Water Pressure valves on the Triaxial Cell Base (Figure 8) and plug the Din plug into the designated socket on the Logger/Instrument. It is important to connect the Transducer to the correct valve on the Triaxial Cell Base (the two PWP valves are directly opposite each other, in line with the two small holes in the Base Pedestal).
1) Ensure the APC(H) is correctly initialised and then connect the tubing to the PWP, see Figure 8.
2) Click on the Pressure Channel Number to display the Channel setup window (Figure 10). In order to enable editing of the Calibration Parameters, the ‘Edit’ button should be selected and the passcode entered.
1) Select the ‘Dual Point’ radio button, set the ‘Zero’ field to the lowest Pressure reading (usually 0) and the ‘FSD’ (Full Scale Deflection) field to the highest reading (in this example 1MPa).
2) To reset the Pressure Channel, click on the ‘Clear’ button.
3) To send the input information to the Transducer, click on the ‘Write’ button.
4) With zero Pressure set at the APC, click on the ‘Zero’ button. The Display will reset to 0 – see Figure 9.
5) Now set the APC to the Maximum Pressure of the Pressure Transducer (in this example 1MPa i.e. 1000kPa) and click on the ‘Gain’ button. The Display will reset to the FSD value (Figure 10)
NOTE: a Reference point must be used to determine zero and maximum pressure.
6) When different pressures are applied, the Display will reflect the pressure accordingly.