Panametrics CTF878, Руководство для стартапов, Страница: 40 / 108

Chapter 2.
32 Model CTF878 Startup Guide
2.1.12 Installing Temperature and Pressure Transmitters
Temperature and pressure transmitters are usually not required with the CTF878 system, but may be installed for
standard volumetric or mass flow determination.
IMPORTANT: Under changing temperature and pressure conditions, the CTF878 can calculate standard volumetric
flow accurately only if temperature and pressure transmitters have been installed.
2.1.12.1 Locating
Temperature and pressure transmitters should be positioned downstream of the clamp-on fixture / transducers, no
closer than two pipe diameters and no further away than twenty pipe diameters.
2.1.12.2 Mounting
Typically, a 1/2” NPT female threaded port is used to mount the transmitters on the pipe. If the pipeline is insulated, the
coupling may need to be extended to provide convenient access. Of course, other types of mounting ports, including
flanged ports, may be used for the transmitters.
Figure 19 below shows a typical mounting arrangement for the pressure and temperature transmitters. The
temperature sensor should protrude 1/4 to 1/2 way into the pipe.
2.1.12.3 Wiring
These transmitters must use a 0/4-20 mA signal to transmit the temperature and pressure values to the CTF878
electronics console. In turn, the electronics console will provide a 24 VDC signal to power the transmitters. Any
transmitters or sensors that are used must have an accuracy equal to 0.5% of the reading or better.
Note: Resistive Thermal Devices (RTDs) are a good choice for measuring the temperature.
To wire the transmitters, refer to Figure 20 on page 33.
Figure 19: Typical Temperature/Pressure Transmitter Mounting
Temperature
Transmitter
RTD
Thermowell
Coupling
Isolation Valve
Flowcell Wall
Pressure
Transmitter