How to select the correct Signal Conditioner
A signal conditioning unit typically converts one type of signal to another more robust and useable type of signal, for example, a mV thermocouple input signal may be converted to an isolated 4-20mA output signal.
Cynergy3’s range of modules can accept virtually any type of process input and generate industry standard analogue, digital and communications link outputs. The range has been designed to be as compact as possible, saving on panel space and allowing units from other suppliers to be easily replaced with one from the Cynergy3 collection.
There are four main applications for Signal Conditioning equipment:
- Elimination of earth loops and AC Electrical noise.
- Signal conversion, usually from a low level signal into a robust high level output.
- Transmitter sharing and loop boosting, the output from one transmitter goes into two or more instruments.
- Elimination of Bucking Power Supplies, in this scenario two instruments both want to supply the power to a transmitter which can lead to transmitter damage.
A single Signal Conditioner can be used to solve all the above problems by providing Isolation, Conversion, Loop boosting and power handling in one package.
Cynergy3 Signal Conditioners typically include an isolating power supply which includes a proprietary isolating transformer built into a switch mode power supply. This enables separate, isolated power rails to be provided for the input, output and power supply stages. Signal isolation is performed either by custom designed galvanic transformers and/or or digital opto-isolators. Typical continuous isolation voltages are 1kV although surge voltages or 2.5kV for 50us and transients of up to 10kV/us can also be withstood.
Typical inputs include AC/DC Voltage and Current, including bipolar voltages, thermocouples including types E,J,K,N,R.S.T & B, PT100 and PT1000 temperature sensors, potentiometers, frequency inputs including PWM and strain gauge/load cell inputs. Outputs are typically mA or DC voltage including 4-20mA, 1-5V, & 0-10Vdc. There are also communication port outputs including RS232, RS485 and TCP/IP Ethernet communications, all using the standard Modbus RTU/TCP/IP protocols.
If alarm outputs are needed both purely analogue or analogue and digital trip amplifiers are available which have main rated relay outputs with adjustable alarm set points and, in some cases, adjustable hysteresis.
The E-100 and Isoslice modules can be used together to provide Modbus registers of up to 1028 parameters, again all these inputs are into isolated input stages and the Modbus protocol is compatible with almost any manufacturer’s PLCs and SCADA or Data Logging packages.
Cynergy3 range of Signal Conditioning products has been designed to be as user configurable as possible, usually through the use of internal DIP switches or free PC configuration software. When DIP switches are used in the Isocon/ Dualcon range there is an interactive PC utility which calculates the DIP switch settings required for any input & output combination. There is also a selection guide which illustrates which product can handle particular input/output requirements. The main considerations when selecting a Signal Conditioner are as follows:
- Power Source, this can be AC, DC or loop powered, where the instrument is self-powered from the in-coming 4-20mA signal.
- Input Signal type, types include AC/DC current & voltage, thermocouples and RTDs.
- Input Signal range, typically 4-20mA or K Type thermocouple 0-1200°C.
- Output Signal type, usually 4-20mA, 1-5 or 0-10V or a communications interface.
- Isolation Voltage required, this is a continuous 1kV for most Cynergy3 units.
- Accuracy, typical accuracies of better than 0.1% FSD are achievable with the Cynergy3 range.