Eurotherm/Barber-Colman 2704 - 1/4 DIN Multiloop Vacuum Controller/Programmer

2704VC

COMBINED TEMPERATURE AND VACUUM CONTROL
NOW POSSIBLE WITH SINGLE EUROTHERM CONTROLLER

By creating a special vacuum control function for its well-established Model 2704 Controller, complex processes like those found in vacuum heat treatment furnaces, may use a single combined function controller to save cost and space.

This multi-function facility will also be useful for similar vacuum related processes such as freeze dryers, autoclaves, semiconductor furnaces and CVD furnaces.

Model 2704 Vacuum Controller

2704 Expansion I/O

Advanced Features
TRIPLE INDEPENDENT CONTROL LOOPS
SUPPORTS UP TO 3 VACUUM GAUGES
VACUUM PROBE SWITCHOVER
HIGH VACUUM GAUGE POWER UP
GAUGE STATUS INPUTS
LEAK DETECTION
ROUGHING PUMP TIMEOUT
GAUGE CALIBRATION
ADVANCED PROGRAMMER
EXPANDABLE I/O
MODBUS RTU or PROFIBUS-DP COMMUNICATIONS

2704 VACUUM CONTROLLER DOCUMENTATION

Unless otherwise noted, the following documentation is in PDF format.


Data Sheet	HA026916 Iss 6 09/2004 (512KB)
Glossy Sales Brochure	HA026750 Iss 2 07/2002 (4,317KB)
Installation and Operation Handbook	HA026502 Iss 5 10/2004 (2,588KB)
Addendum to User Guide	HA026502 Iss 4 06/2003 (583KB)
Engineering Handbook	HA026933 Iss 5 09/2004 (7,729KB)
OEM Security Engineering Handbook Supplement	HA027482 Iss 1 07/2001 (56KB)
Low Voltage Addendum	HA026502 Iss 2 12/2000 (8KB)
Vacuum Furnace Controller/Programmer Data Sheet	HA027551 Iss 2 08/2002 (242KB)
Vacuum Furnace Handbook Supplement	HA027655 Iss 2 08/2002 (1,867KB)
Vacuum Control Handbook Supplement	HA027186 Iss 1 08/2000 (158KB)

Technical Notes
TIBC149 - Downloading 2704 Vacuum Curves (60Kb)

Other Related Pages
Click here to go to the 2704 page.

PRODUCT APPLICATION

Complex heat, pressure and vacuum cycles, such as those found in advanced heat treatment furnaces, usually require the use of high specification programmers or PLCs. In such cases the temperature control function alone may be handled using one or more temperature controllers, either in cascade or single loop mode. Sometimes where vacuum bags are used, pressure can also be regulated by the same controller.

However, In addition to separate temperature and pressure control facilities, systems of this type will also usually have a dedicated vacuum control unit, designed and built to traditional standards, adding considerable cost and bulk to the equipment.

Model 2704 Vacuum Controller

The introduction of the 2704 vacuum option has enabled Eurotherm to integrate both the temperature and vacuum control functions into one unit, providing both OEMs and heat treatment specialists with a more economic and compact control solution than they have available at present. Removing the need to buy separate expensive vacuum controllers can reduce the size of a system control PLC, or in some cases remove it completely. Eurotherm claim that the 2704 is the first DIN format temperature controller to offer this feature.

Operationally, the use of a single 2704 in this type application can offer clear advantages in processing efficiency. The unit provides provides a more informative display than more traditional vacuum control units, and in addition provides a smooth switchover function between high and low vacuum levels. This function is not generally available with traditional designs of vacuum controller, a weakness which has been known to cause problems within some heat treatment processes. The 2704 vacuum function is available in two levels:

The 1-Gauge option (V1) provides an input for a single vacuum gauge, six on/off setpoints, roughing pump timeout, leak detection and a vacuum summary page.
The 3-Gauge option (V3) provides all the facilities of V1 plus the facility to measure two other gauges.

As part of the V3 option, one of the additional gauge inputs is directed at high vacuum gauges which need to be powered off at low vacuum in order to prevent damage to the sensor. A dedicated gauge switchover software block allows both high and low vacuum gauge inputs to be used for a 'bumpless' measurement of the chamber vacuum.

The vacuum function also incorporates a number of vacuum-specific measurement and display options, including displays in scientific notation ( range 9.99E-9 to 9.9E+9), a Log10 input option for gauges with logarithmic type responses, storage of process specific sensor linearisation tables, and selection of the programmer mimic as either a main or summary display page.

Technical Notes

Of the many techniques that are used to evacuate vacuum chambers, the most common is the use of a diffusion pump, although the cryogenic pump is now growing in popularity. When using a diffusion pump it is necessary to place it between the furnace chamber and a mechanical rotary (roughing) pump. The area between the diffusion pump and the mechanical pump is referred to as the backing chamber.

The mechanical pump reduces the backing chamber pressure to below the maximum intake pressure of the diffusion pump. Only when this low level of pressure is achieved can the diffusion pump start to operate correctly.

In a typical single chamber furnace system, there will be three vacuum gauges: In the main vacuum (or furnace) chamber there will be two gauges, one for low vacuum (pirani gauge>10 -3 mB) and the other for high vacuum (Active Inverted Magnetron AIM) gauge <10 -8 mB. The backing chamber gauge, another Pirani, is treated as a separate input.

The two main chamber gauges will be required to perform an automatic switchover, similar to the way in which thermocouple & pyrometer sensors are required to switch at high temperatures. Both types of vacuum gauge (each of which require a 24vdc power supply) give a 2-10vdc logarithmic output covering separate vacuum ranges. Most common units are calibrated in mB, Torr or Pascals. In order to be able to display high vacuum values to the operator, scientific notation is always used, and this function forms part of the 2704 vacuum option.

In a typical sequence, a plc in conjunction with the vacuum controller will isolate the backing chamber from the furnace and switch on the backing pump. When this chamber reaches a set vacuum, the plc will change its interlocks to enable the diffusion pump to evacuate the furnace. Again when the furnace reaches a set vacuum, the plc will allow the designed temperature profile to begin, while continuing to monitor that the necessary vacuum is being maintained.

The JAVA Applet below enables you to create a configuration string for the Model 2604 and 2604f. Select the options you require from each field from the drop-down list box. Invalid choices are displayed with an error message in the text box at the bottom of the Applet.

Last Updated Monday, September 05, 2005