The new SSRTC mounts directly on the input terminals of a Solid State Relay and provides a low cost, conveniently packaged temperature control solution. The input accepts J or K type thermocouples and can be used on heat or cool processes with on/off or proportional control. The setpoint can be controlled by a potentiometer or analog voltage or analog current. The temperature setpoint is proportional to the voltage or current at the setpoint input. Status indicators indicate how close the temperature is to the setpoint.
We get many calls from customers that want to control the temperature of a process without a closed loop temperature controller. In this mini article we will briefly discuss open loop temperature control vs closed loop temperature control. First, lets simply define closed loop and open loop as it applies to common electrically heated processes:
Close loop temperature control utilizes a temperature sensor that monitors the process. This feedback is fed to a temperature controller which controls a Power Controller that will apply power to the heater precisely and maintain the process temperature. Some of the advantages of closed loop control are accuracy, repeatability, fast warmup times and fast recovery times.
Open loop temperature control does not utilize temperature feedback from the process. The power delivered to the heater is set by the user, usually with a potentiometer and SCR Power Controller or a Variac (variable auto transformer). Some of the advantages of open loop control are simplicity, low cost, reliability.
One of the major advantages of NuWave SCR Power Controllers and SSR Driver Boards is line voltage compensation. Line voltage compensation corrects for changes in line voltage. Performance improvements can be observed in closed loop processes, but especially in open loop processes.
If you have a process where the temperature accuracy is not critical, open loop control may be an option. The only way to really tell if open loop control is suitable is to try it in your process and see if the results are acceptable.
The Staging Control with Verneir – NWVS is a step controller that provides modulation in multi-stage applications such as duct heaters. The built in 0-10V Vernier stage output allows for smooth, precision control of the load. When the verneir output is connected to an SSR or Phase Angle Controller – SSRMAN-1P it will increase the precison of the heat control without reducing the life of the system contactors. The unit’s LEDs show the power and output status of all of the stages including the vernier output.
Our new small temperature controller – MicroTC is our smallest and lowest cost temperature controller. The MicroTC is factory set for your setpoints and hysteresis. A version is available with setpoint adjustment from an external potentiometer. The small MicroTC is available in 12V and 24V versions and provides a 3 Amp MOSFET output that can be used to drive an SSR ( solid state relay) or small heater. The integral small solid state temperature sensor eliminates the cost of an external thermocouple or RTD.
The new ZERO CROSS SCR GATE DRIVER NWZC-SCR, is a low cost SCR driver for driving back to back SCRs in resistive load applications. The driver board is zero cross fired and has on board MOV protection. It provides optically isolated 5V, 24V inputs that can easily be interfaced to temperature controllers and PLC Time Proportiong (PWM) outputs. The packaging is available in panel mountable or din rail mountable snap tracks.
SCRs requiring 200mA of gate current or less are a good fit for use with the ZERO CROSS SCR GATE DRIVER NWZC-SCR. Wiring of the Module is simple and requires no external power supply; the gate drive power is derived from the line supply of the SCRs.
Controlling TECs or Thermo Electric Coolers with standard off-the-shelf temperature controllers presents a challenge to the system designer. Pelteir devices require H-bridge drivers to provide heat and cool functions. The H-Bridge has to be designed to allow the heat and cool outputs of the temperature controller to steer the correct polarity of the DC power source into the TEC. The new TEC H-Bridge TCH1560 Isolated H-Bridge Amplifier makes the design task much simpler.
The temperature controller outputs interface directly to the optically isolated input as shown above. The power input is connected to the Thermo Electric H Bridge Controller TCH1560 and the TEC is connected to the output. Special shoot through prevention logic prevents the outputs from turning on at the same time even if both temperature controller outputs are on. With a frequency response time as fast as 1mS and a 60V 15Amp rating the TCH1560 presents a high performance and economical way to drive TECs in a heat cool configuration.