Appendix I
GENERAL PURPOSE INTERFACE BUS (GPIB)
GPIB control of the Series 850 TEC Controller is accomplished through a GPIB to Modbus
converter. This converter takes two simple GPIB commands and allows complete control over the Series
850 TEC Controller through the use of the MODBUS protocol using RS485. RS485 is one of the standard
communications protocols used to communicate to the Series 850 TEC controller and allows multiple
devices to be configured on the same I/O lines. Therefore, both RS485 and GPIB are available when
GPIB is ordered. The RS485 is connected to a 9 pin female “D-Subminiature” connector on the rear of the
Series 850 TEC Controller. When shipped from the factory in this configuration, the Series 850 TEC
controller is set up so that the GPIB address is “04” and the MODBUS address is “01”. Both of these may
be changed if necessary and are described in detail in this appendix.
Please reference the Modbus section of the Manual in Appendix K for more information on the
MODBUS protocol for use with RS485. Please note that references to MODBUS registers are necessary
to use the GPIB Read and Write commands described in this appendix.
Follow these simple steps to start communicating with the Series 850 TEC Controller via GPIB.
1. Verify that the default address of “04” is appropriate for the GPIB bus that the Series 850 TEC
Controller will be connected to. If not, please refer to the “Changing the GPIB address” on page 90
later in this appendix.
2. Connect the Series 850 TEC Controller to the GPIB bus with an appropriate GPIB controller set up to
“talk” to the address currently assigned to the Series 850 TEC. Default address is “04”.
3. Turn on the Series 850 TEC Controller and verify that the controller is operational by sending the
“*IDN?” query. The Series 850 TEC Controller should respond with the controller’s IDN message.
4. The Series 850 TEC Controller should be ready to communicate at this point. Basically, only two
commands (Read and Write) are needed to communicate with the Series 850 TEC Controller. These
commands are described in detail on the following pages.
5. Get familiar with the MODBUS commands and register numbers listed later in this chapter. The most
frequently used commands / registers are listed for your convenience.
For those instruments equipped with the GPIB interface, a communications port is available to facilitate
communications with the Series 850 when GPIB is not being used. The default port type is RS-232/D, and
the communications signals are present on the DB-9 connector below the GPIB connector. The factory
installed RS-232/D can be replaced with RS-485 at the factory if specified by the customer at time of order.
There is a two position switch mounted just to the right of the DB-9 connector which selects the source of
the control signals to the Series 850 controller. When the switch is in the UP position, the GPIB device
supplies control signals to the controller. When in the DOWN position, the serial communications port
supplies control signals to the controller.
ALPHA OMEGA INSTRUMENTS CORP. Instruction Manual
Series 800/850 Thermoelectric Cooler Controller Page 85
To Next Page
Loading...
Need help?
General