Control ABB VFD through RTD 250ohm directly on water temp
in my opinion:
1. first convert RTD (a transducer) to a sensor, for which you can design a instrumentation amplifier using opamp, or use wheatstone bridge with RTD on test arm, balance the bridge by adjusting variable resistors on other arms & take the wheatstone o/p signal & connect is to an amplifier (preferably an opamp, so, that its, min & max range o/p current range become 4mA to 20mA) & you can connect this sensor signal to analog I/Os of variable frequency drive.
Or,
if considering to use a PLC than use ABB SLC500 you can use parameter block to set the i/p temperature ranges & current ranges in it & use the PLC I/Os to be fed into analog I/Os of your ABB VFD.
Or,
If you consider a microcontroller, that you can use an ADC (I2C or SPI based) connected to MISO (in case of SPI bus) or SDA in case of I2C bus, can read the RTD amplifier setup (the sensor O/P i have suggested above), & you can feed VFD analog I/Os with microcontroller I/Os according to your need.
1. first convert RTD (a transducer) to a sensor, for which you can design a instrumentation amplifier using opamp, or use wheatstone bridge with RTD on test arm, balance the bridge by adjusting variable resistors on other arms & take the wheatstone o/p signal & connect is to an amplifier (preferably an opamp, so, that its, min & max range o/p current range become 4mA to 20mA) & you can connect this sensor signal to analog I/Os of variable frequency drive.
Or,
if considering to use a PLC than use ABB SLC500 you can use parameter block to set the i/p temperature ranges & current ranges in it & use the PLC I/Os to be fed into analog I/Os of your ABB VFD.
Or,
If you consider a microcontroller, that you can use an ADC (I2C or SPI based) connected to MISO (in case of SPI bus) or SDA in case of I2C bus, can read the RTD amplifier setup (the sensor O/P i have suggested above), & you can feed VFD analog I/Os with microcontroller I/Os according to your need.
