I am trying to utilize the two analog inputs on my Allen Bradley Pico
Controller model 1760-L18BWB-EX to measure pH and temperature levels
in a water quality monitoring application. The analog inputs have a
standard voltage range of 0-10V DC. I am having trouble finding any
electrodes for pH or temperature measurement which would work in a
submerged application. I am interested in an inline electrode or a
probe style electrode as long as the size is limited to below 6in in
length and 1in diameter. Does anyone have any suggestions of
I have used a few different brands, some with little success and some with a
lot, on a wastewater plant some time back. I suggest you buy separate pH
and Temperature transmitters and wire the 0-10V analog output back to your
For pH, I recommend the ABB 4600-series instruments - these are easy to set
up and use, but the probes are a bit bigger than your spec (6.1" long and
1.1" wide) To be fair, ABB do have a range of lab electrodes that are
smaller than this, but they are glass and a lot less rugged. (Do a Google
search on "ABB 4630 pH")
For Temperature there are a few companies to choose from - I would recommend
you start with Rosemount, but ABB sell temperature transmitters too...
Hope this helps,
Any suggestions on temperature transmitters? I am looking for a low cost
solution for a few dozen temperature sensors. My system is VME based,
but there is very little available for temperature measurment in VME
cards. So I am looking for a transmitter which can (idealy) provided a
0-10 V linear analog out to feed to a VME A/D board. My temperature
range of interest is only 20-100 C and I'd like resolution of 0.1 C, so
I'm looking towards thermistors. The sensors need to be surface
mountable, small, non-magnetic and be located in a radiation-controlled
area. The transmitter can be located outside the radiation shielding if
Anyone have any suggestions?
Actually, I have nearly 500 DS1820 digital thermometers in "1-wire"
networks using ascii RS-232 to 1-wire adaptors. These don't have quite
enough resolution for this particular application. Moreover, they have
proven to be very unreliable for us (not the sensors themselves so much
as the 1-wire network). This is at least partly to do with poor
installation on our part, but our overall experience has been bad
enough that we are unwilling to invest more into these.
Some more details on our setup: this is a particle accelerator
(electrons) facility. These temperature sensors are a first line of
machine protection for electromagnets, UH-vacuum beam pipes, an RF
system, etc. The control system is already in place (primarily
VME based) which can provide archival, alarm notification, remote
display, etc. I'm looking for a few dozen temperature sensors (20-100
C, 0.1 C resolution) with a reasonably easy way to interface to our
control system. A sensor -> VME module would be ideal, but
sensor -> transmitter (0-10V) -> VME A/D would be good (already have the
VME A/D available).
GLI (Great Lakes Inst) and Hach I think both have pH instruments which also
put out the stream temperature, both as 4-20ma. You need the temp to make
properly corrected calulations or interpretations of the pH readings.
4-20 mA is the standard for transmitters. Put a 250 ohm resistor at your
input. Place a 24 VDC power supply in series with your transmitter and then
run it to the resistor. Connect the negative of the power supply to the
neutral of the AI. Now you have a standard 1-5 VDC signal. Ignore any
values outside this range.
Try the Omega catalog for a great range of relatively cheap instrumentation
including pH and temperature transmitters.
0.1 C resolution is pretty tough to get. A direct 3- or 4-wire RTD input
would be much better.
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