The minimum voltage required is determined by Ohms law, V-IR (voltage equals current times resistance). The only limitation for the number of instruments is the amount of voltage from the power supply driving the current loop. Instrument calibration and troubleshooting are simple in a multi-instrument current loop. For example, a material test center may have one control room for all the different test labs, enabling operation from one central location. Long distance transmission from instrument to instrument without electrical interference make multi-instrument systems easy. One of the great advantages of a current signal is the simplicity in setting up a multi-instrument system. This diagram illustrates the correct wiring. The fact that they can transmit signals over long distances without interference makes it easier to connect a milliamp-signal device to multiple instrumentation units. Pressure transducers that output milliamp signals can connect to multiple devices in series. WIRING ONE TRANSDUCER TO MULTIPLE READOUTS, RECORDERS, COMPUTERS, ETC. Converting current into voltage for instrumentation set up for voltage Multiple transducers wired to one meter and one switch (transducers with built-in zero & span adjustments, same outputs & same pressure ranges)įigure 7. There is also nothing wrong with powering just one transducer with a power supply having high current capacity.įigure 6. For example, if you have 50 transducers drawing 13 milliamps, you will need a power supply having at least 650 milliamps (50 x 13). The sum of the current draw of the transducers can not exceed the total current capacity of the supply. The number of transducers that can be used is simply determined by the current draw of each transducer and the current capacity of the supply source. Multiple transducers can be excited from one power supply. When installing transducers, refer to standard industry torque data for thread size and material type.įigure 3 DETERMINING HOW MANY TRANSDUCERS CAN BE EXCITED FROM ONE POWER SUPPLY Installation - Installation should be made only by qualified personnel familiar with safety practices and knowledgeable with all industry accepted standard relating to pressure systems.Transducer calibration and/or zero may shift if it is over-torqued when installing. Avoid locations with excessive vibration. The temperature coefficient effects on the overall accuracy of the transducer can be minimized the closer the ambient temperature is to 25☌. Ambient temperature should be within the transducer specifications. Operate at Ambient Temperatures- Locate the transducer where it can be readily inspected and serviced. Use pressure limiters, capacity chambers, snubbers, etc., if needed. Make sure you have the correct thread type and size fitting. Fittings and Hardware - Use appropriate pressure rated fittings and hardware. Diaphragm - Do not press or touch the diaphragm as you may damage or alter its calibration, particularly on low pressure range models. HANDLING, LOCATING AND INSTALLING TRANSDUCERS Figure 2 Typical wiring configurations are shown in Figure 3. A current signal also can be transmitted long distances. Unlike the millivolt and voltage output transducers, a current signal is immune to any stray electrical interference, a valuable asset in the factory. Again, due to the built-in signal conditioning, the transmitters are higher cost and larger in size than the millivolt output transducers. A transmitter produces current output only. Typical wiring configurations are shown in Figure 2.Ī transducer produces millivolts, amplified voltage, or current output. Amplified voltage signals can travel up to medium distances and are much better in their immunity to stray electrical interference than the millivolt signal. Due to the built-in signal conditioning, they are higher cost and larger in size than the millivolt output transducers. Transducers with an amplified voltage output are generally used in a light industrial environment and computer interface systems, where a higher level dc signal is required. Typical wiring configurations are shown in Figure 1. Remembering that the millivolt signal is very low level, it is limited to short distances (up to 200 feet is usually considered the limit) and is very prone to stray electrical interference from other nearby electrical signals (other instrumentation, high ac voltage lines, etc.). They are low cost, small in size, and require a regulated power supply. Transducers with a millivolt output are generally used in laboratory applications. TRANSDUCER OUTPUTS AND THEIR WIRING CONFIGURATIONS The following will describe the advantages, disadvantages, and wiring for millivolt, volt and current output transducers. It is important for the user to know which output suits his application to ensure proper selection of a transducer. OMEGA transducers have three main types of electrical outputs millivolts (mV), volts (V), and current (mA).
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