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
