Converting a Voltage signal to Vacuum reading

[Brian123]

I was disappointed when MKS didn't have a sensor for our pressure ranges that spoke modbus (I don't think any of their stuff does, or at least did). Writing a custom ASCII protocol driver was a bit of a pain, but I wanted to keep a logarithmic analog conversion out of my sensor feed. I agree that sensor suppliers could do more to make their products easier to use.

Brian

 

[NetNathan]

I mainly use capacitance manometers when I have a process gas that I need to control precisely. The cap. manometer is not dependent on the gas molecular weight so its an ideal fit for that application but less than ideal for straight vacuum. For hi-vac I use convectron + ion gauges. Lesker has a new instrument that combines a convectron and ion gauge in a single gauge/controller combination - haven't used it yet but it has potential. I've used Granville-Phillips gauges with device-net interface and been pleased with the results. G-P is now a part of MKS. I've only used the Televac multichannel controllers but their stand alone gauges are intriguing.

I still haven't seen any manufacturers producing gauges that talk ethernet/IP. End users are tired of not being able to easily and accurately log vacuum data, but for some reason the vacuum industry has been ridiculously slow to clue in.

I am very impressed with Televac instrumentation.
I have used many of Televac standalone gauges. The new MX4A Convectron is a very nice unit, especially since it also offers true linear out from 1 Torr or 10 Torr to 1 micron (1x10-3 Torr) and log. The MP7ER Cold Cathode is very durable with analog out for log-linear, log and 3 decade true linear.
It is very nice having the pressure readout on the gauge.

I have also used the Inficon BCG450, which is a nice combination gauge, with built in readout, that operates from 1125 to 3.75 x 10-10 Torr. It supports RS232, and options for RS485, Devicenet, and Profibus. I have used it with Ethernet/IP, but using an Anybus module for the RS232 to Ethernet/IP conversion.
It has an Analog out also....but it is straight Log??? All that power and still no linear analog out.

 

[TConnolly]

Any thoughts on Televac's CC-10 wide range gauge? It reads from 760 to 10E-9 torr in a single device. Atmosphere down to 20 millitorr is read with a quartz oscillator instead of a convectron, Piranni, or TC gauge. From 20 millitorr down to 10E-9 torr is read with a double inverted magnetron cold cathode gauge. I normally use Bayard-Alpert ion gauges and have never used a CC gauge so I've been leery about committing to one. CC gauges used to have accuracy and repeatability problems, but I think much of that has been worked out. I've actually got a project going now to replace furnace control system using GE + Yokogawa with a ControlLogix.

 

[NetNathan]

In the heat treat industry the convection range seems to get the most abuse because of what is in the atmosphere in those ranges. I just do not know about the durability of a "quartz oscillator"in a heat treat furnace atmosphere.
I can get Televac to supply me one for testing. I got one of the first MX4A convectrons for testing when it first came out. I know the people at Televac very well. I have been specifying/selling/installing/troubleshooting them for over 30 years.
I am sort of apprehensive about combined gauges unless they are completely rebuildable. I do not think the CC-10 is but at least it offers a true linear analog out.

the Inficon BCG450 can be fully rebuilt, having the ability to replace either the "Convectron Enhanced Pirani", Capacitance Manometer, or Ion gauge sections. I am getting a "combined range" that is true linear from all the sensors. However the RS232 signal is in High Byte, Low Byte form and also needs a Bit Shift done after you combine the high and low byte........what a lot of logic to assemble the reading???
The great thing about this is Anybus did the complete conversion for me in their RS232 to Ethernet/IP converter. So I get a nice full linear range in Torr read into the ControlLogix processor as a DINT . (Daba wrote a great AOI for me that converts it also into scientific exponent.)
I get another DINT that gives me status of the gauge and status of each sensor.
Another DINT gives me some control of the gauge configuration and operation.

I have the Anybus configuration and the AOI if you ever want to test this unit out.