Pakarab fertilizers limited multan
Download 3.37 Mb. View original pdf
|
- Navigate this page:
- 7.7 Sensor Troubleshooting
- Temperature Calibration
| 7.6 Wiring Cable Length When a internal preamplifier is used, the analyzer/transmitter can be up tom ft) away from the sensor. If no preamplifier is used, the distance is limited tom ft. Wire A is not present on the cable of a sensor with a wire RTD. Wire A on patch cords used with sensors without preamplifiers is only functional when the sensor contains a wire RTD. Do not connect wire A to the analyzer/transmitter tape it back) if the sensor does not contain a wire RTD. Wire A is not used with 873 Analyzers. In such applications, it should be taped back. 126 Field Instrumentation GEN Rev) 7.7 Sensor Troubleshooting 127 Field Instrumentation GEN Rev) 7.8 Maintenance Calibration: Sensor and analyzer/transmitter system should be calibrated regularly. A sensor loses calibration for two general reasons the slope changes or the offset changes. Slope changes are usually due to aging of the measuring electrode. Offset changes are often due to clogging and contamination of the reference junction. A single point calibration corrects the offset only. A two point calibration corrects both the offset and the slope. Frequency of calibration is dictated by the rigors of the process, such as temperature, pressure, abrasives, harsh chemicals, and so forth. It is also related to your requirement for accuracy. Many users do a single point, grab sample calibration frequently and a two point calibration only occasionally. Temperature Calibration Dolphin sensors include a precision temperature measuring element. Foxboro analyzers and transmitters use this temperature measurement to provide automatic temperature compensation of the pH measurements. ORP measurements do not require temperature compensation. For optimum pH measurement accuracy, the temperature measurement accuracy should be checked and adjusted if necessary. This is especially important when along cable length is used with sensors that have wire RTD elements. Sensors with wire RTD elements automatically compensate for errors due to cable length. Refer to your analyzer/transmitter instruction for specific calibration procedures. Download 3.37 Mb. Share with your friends:
|