Instrumentation pH, Viscosity, Acidity


Thread Starter

Antonio Martinez

Hello everyone,

I have a process control system SLC 5/05 controlling the production in a continuous mixing line for the food industry. I want to monitor in this control system some variables in the finished
product pipe, while the product is flowing:
* Acidity
* pH
* Viscosity

My question is if any colleague had ever faced similar target and had good/bad experiences with some brands or equipment, because we never did in the past. Until today, we only rely on lab results. But times change and I'm sure today's technologies can do this work better, faster, and they are more reliable.

Please include the brand name brand/model with your response. Each should have the following:

1. 4-20 mA output is mandatory
2. Food grade
3. Sealed housing to protect from splashing, resistant to pressupre
(2 to 4 bar)

If you are a vendor you should reply directly to my email address instead of this forum as it will needlessly tie up these other folks time and efforts. Thanks for your help.

Antonio Martinez

[email protected]
pH is a/the measure of acidity/alkalinity, so measuring pH will inform you about how acidic/basic your product/process solution is. To
measure pH in-line you will need a transmitter (electronic unit/analyser) and a probe. Transmitter from any vendor will work fine,
less or more almost all transmitters have the same
functions/capabilities. You can use transmitters and probes from different vendors interchangeably. My idea is the new series of
transmitters from Mettler-Toledo will just face the needs offered at prices as low as 500-600$, still as functional as the others.
Probe is the actually real critical part of the pH measurement. There is no single probe that you can use for all applications and
processes. Choosing the most suitable probe for any application is a real optimisation problem btw. cost, accuracy, life and performance. A
vendor is best in some applications, while the other in some other applications. You should detail your application more (liquid/solid, pH
range, amount of sulphides, proteins and some other ions contained, temperature, pressure, conductivity, etc. ), in order someone to offer
you a probe, this is also the case with manufacturers, they need many data before they can offer you a probe.
Relaying on our past experience (bad/good), we used products of almost all main pH vendors, I can say that probes of Mettler-Toledo or Broadley-James will offer you the best in terms of performance/price ratio. But as I said this is very depended on type of your application. I can also advice TBI-Bailey (I think currently ABB-Bailey).

For the viscosity, about a dozen of principles are available. Two of them are worth mentionning:

1 . Viscosity sensitive rotamaters (Fisher Porter)
2 . Pressure drop through friction tube (Hallkainen, Precision Scientific).

What about measuring consistency, instead ?
[email protected]

Gary Norwood

I can agree with the ABB/Bailey for pH. We currently use them and have had good results. They make one of the most durable pH probes around. Inline Viscosity can be measured/calculated using a Micromotion flowmeter along with a differential pressure transmitter. We have looked at the application but not implemented. It should work.