TURTLE
TOUGH
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TT-MA-CON measurement transmitters?
This will really depend upon your particular data acquisition and control setup. One thing to keep in mind is that the resolution of the
TTMA analogue output is fixed at 1000 steps completely independent of the scaling selected. This means that you have the same
number of steps if you define your output to be the full range or a much narrower portion of that range down to the minimum scaling
allowed for that module. As an example, if you have a TT-MA-CON transmitter suitable for use with a 1.0/cm cell constant you maxi
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mum full scale range would be 0-50,000 microSiemens and the minimum scaling would be 0-5,000 microSiemens. Since the output
resolution is fixed independent of scaling, choosing the minimum range would give you ten times (10X) better relatively resolution in
absolute microSiemens (5μS vs 50μS in this example).
As another example the full range scaling for the TT-MA-pH in the pH measurement mode is 0-14. If your application should truly only
need to operate between the pH range of 4 to 11, then you relative output resolution would double by restricting it from the full range
0-14 to the more narrow 4-11 scaling since we have gone from a total of 14 pH units to only 7 pH units while the absolute output
resolution is fixed. For most TT-MA measurement module the scaling can be reduced down as low as 10% or 20% of the full range.
Check the relevant TT-MA transmitter specification sheet and manual to find the specific limits of your module (be sure to check
revision number). Depending upon your needs it may then be advantageous to restrict the output scaling to the typical minimum
and maximum operational range for that measurement point to have the highest possible resolution on the analogue output of the
corresponding TT-MA module. As discussed in the previous Question & Answer above, if you change the output scaling (and thus the\
resolution) from the measurement transmitter you will also need to be sure to change the input scaling for any mating modules (such
as the TT-MA-REL or TT-MA-TOT) that use the analogue output from this measurement module. Most of the TT-MA measurement
modules with the MODbus output option will follow the analogue 4-20mA scaling and the resolution is also fixed at 1000 steps by de
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fault. The MODbus protocol does allow for the possibility of much higher resolution output. One example is the TT-MA-pHE module
with 20,000 steps giving\ a resolution of 0.001 in pH mode and 0.1mV units in ORP mode. As another example, the TT-MA-CON-E
offers between 10,000 and 20,000 steps for the temperature compensated conductivity and 50,000 steps for the raw conductivity
values giving the high possible resolution anywhere in the range for a given cell constant (see separate TT-MA-CON-E cut sheet for
details). Note that the temperature is always sent as 1,000 steps no matter the TT-MA transmitter employed. Lastly, all of the mea
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surement modules (TT-MA-pH, TT-MA-ISE, TT-MA-CON, TT-MA-DO and TT-MA-TOT) are compatible for use with the TT-MA-DAT
MODbus datalogger except for the special high resolution MODbus TT-MA-pHE and TT-MA-CON-E units, although these units ARE
compatible with the free of charge Windows software and most any modern MODbus PLC system.
The TT-MA-TOT wiring looks complicated. Will it be hard to use this total ISE measurement module?
While the documentation on the TT-MA-TOT module is exhaustive and thorough, this is primarily for the purpose to allow further
customization by those that have very specific application needs. All of the wiring and configuration is performed at Turtle Tough when
this module is fabricated as part of a complete total ISE measurement system. Bearing the Turtle Tough pre-configuration in mind,
there is typically very few parameters (if any) that need to be changed by the most users. Normally that needs to be done is to connect
the sensor inputs as shown (all other module wiring will be completed prior to dispatch).
Can I add MODbus to the TT-MA-pH, TT-MA-ISE, TT-MA-DO or TT-MA-CON if purchased as analogue output only units?
No. The only option if you need MODbus output for module based as analogue only units is to use a TT-MA-TOT module which
can convert the analogue output to a MODbus output for selected configurations. The only other option is to purchase the identical
measurement module(s) with the desired MODbus output and to change out the existing analogue only units installed (be they in
an enclosure assembly or on a DIN-RAIL). Since the TT-MA-DAT datalogger only accepts MODbus input, if you believe that you may
want to use this field measurement modules with the MODbus output in such cases.
Can the TT-MA-pH and TT-MA-ISE interface pH/ORP/ISE sensors with and without preamplifiers?
Yes. More specifically, the TT-MA-pH can interface pH or ORP sensors ONLY WITHOUT PREAMPLIFIERS and the
TT-MA-ISE can interface ISE sensors ONLY WITHOUT PREAMPLIFIERS. Conversely, the TT-MA-pH-X can interface pH and ORP
sensors ONLY WITH PREAMPLIFIERS and the TT-MA-ISE-X can interface ISE sensors ONLY WITH PREAMPLIFIERS. Note that by
“ONLY WITH PREAMPLIFIERS” this can mean either that the sensor itself has an integral preamplifier or else that a sensor without
an integral preamplifier is bridged across an external preamplifier (see separate documentation for mini external preamplifier option).
Note that the two types of pH/ORP transmitters (TT-MA-pH & TT-MA-pH-X) and ion selective transmitters (TT-MA-ISE & TT-MA-
ISE-X) are altogether different hardware versions and so are not interchangeable in the field. The decision regarding whether you plan
to use a pH/ORP/ISE sensor with or without a preamplifier will need to be known prior to purchasing any pH/ORP or ISE measure
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ment system using TT-MA transmitters so that the suitable type of pH/ORP/ISE transmitter can be selected. In particular be sure to
know the precise cable lengths needed prior to any commissioning for new installation sites and to double-check the required cable
lengths for any existing locations. In the case that you wish to have the flexibility to support long cable runs and/or to the benefit
or noise rejection from the process equipment by using an integral or external preamplifier, you can always choose to purchase the
preamplifier style (TT-MA-pH-X & TT-MA-ISE-X). The pricing is identical for both hardware versions as all software and functionality
is also perfectly identical. Lastly, note that only pH/ORP/ISE sensors with integral preamplifiers can be supplied with quick disconnect
terminations (see separate write-up on this option if this feature is desired). Note that the quick disconnect option must be chosen
at time of order.
Can I change the ion to be measured on the TT-MA-ISE or TT-MA-ISE-X ion selective transmitter?
