4-20mA
Digital Indicators for safe and hazardous areas
- Loop-powered 4-20mA input
- Tough impact-resistant field
units with separate terminal compartments
- DIN-standard panel-mounted
versions
- Environmental protection
ratings to IP65 or IP66 (MTL686)
- Easy on-site configuration
with built-in references
- 'Built-in' linear or square
root options
- Manual control from hazardous
areas provided by set-point generator options
- Wide range certified as
intrinsically safe 'simple apparatus'
- MTL686X for safe area installations
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MTL680 Digital
Indicators enable process variables to be displayed locally
in hazardous and safe plant areas. All versions are loop-powered
from 4-20mA signals. In total, the range includes nine models.
Applications The low voltage
drop of the indicators allows them to be installed in almost any
2 wire 4-20mA transmitter loop. Alternatively, the indicators may
be signal powered. For example, the re-transmission of mass/flow
computations from the safe area, through a suitable MTL IS interface
to the indicator in the safe area. All units can indicate measurements
in either a linear or square root extraction mode, the latter being
used, for example, to display directly the flow from differential
pressure measurements using an orifice plate, Dall tube, or venturi.
Large 3 1/2- or 4 1/2-digit liquid crystal
displays make process variables easily visible at a distance.
A label defining the appropriate engineering unit is attached to
the right of the display. All indicators can be set up to reverse
the 'display direction', ie, to produce a decreasing displayed value
for a rising input signal. Unmistakeable 'error' displays register
out-of-range inputs.
Field mounting units are housed
in tough impact-resistant GRP casings designed to withstand the
rigours of hostile weather conditions and harsh industrial environments.
Protection ratings are IP66 for the MTL686, MTL686X and MTL686-SP
and IP65 for the MTL681B and MTL682B. They can be mounted directly
onto flat surfaces or, with an optional PIP68 kit, onto vertical
or horizontal pipes or posts.
Panel mounting units are designed
for DIN standard 72 x 144mm cut-out. The front panel fascia is protected
to IP65 while, with standard 'snap-on' mounting clips, the panel/unit
seal is rated IP40. The latter can be uprated to IP65 with the optional
IPK68 sealing kit.
On-site configuration for all
models is carried out without recourse to external references by
using built-in reference voltages equating to 4 and 20mA for setting
zero and full-scale values (span). Keypad configuration is a major
advantage for the MTL681B, MTL682B, MTL683B and MTL684B. On MTL686,
MTL686X, MTL686-SP and MTL688 models, all parameters are set by
internal jump links and precision 10-turn potentiometers.
Set-point generation - for manual
control of processes from within hazardous areas - is provided either
by the standalone MTL686-SP or by the SPG68 used in conjunction
with the MTL683B, MTL684B and MTL688. Invaluable for simple operations,
such as 'mixing', that can be controlled from within the hazardous
area, a 10-turn potentiometer is rotated to change the value, displayed
on the associated indicator, of the parameter which controls the
process to make any immediate changes necessary. The set-point generation
function also provides a convenient method of bringing a controlling
4-20mA signal from a hazardous to a safe area.
MTL680 Series intrinsically safe indicators
are classified as 'non-energy-storing simple apparatus' ('non-voltage-producing'
in the USA). These indicators can be inserted directly into any
IS loop without further certification.
Data
Sheet
