This instrument is used especially for processing of output electric signals from different sensors. The electric signal – current or voltage – is converted into a digital form and then it can be displayed on the LCD display, it can be digitally compared with the pre-adjusted level and switch a contact relay or an output of the open collector type on the output. The digitalized value can also be read through the communication interface RS232, RS485 or USB. According to requirements, the instrument can perform just one of the above mentioned functions or a combination of two or three supplementary functions. These instruments can be used everywhere where an exacting measuring and control system is not necessary or a big measuring system has to be supplemented with local display or signalization or if the data have to be transferred into the central computer in the digital form. High cover IP65 and wide temperature range come in useful especially in heavy operations.
All components are situated in a sturdy case from aluminium alloy which secures good mechanical and electric resistance. The inspection window is made from polycarbonate. The case is fixed by means of two holes for bolts which are accessible after opening of the cover and are situated inside the sealed space. An internal terminal board for a cable with a metal bushing PG-9 is used for electric connection. Use of the sealed arrested miniature connector DIN 43650 – C with a cable inlet PG7 is limited for cases of connecting max. 3 conductors.
Electronics is realized by means of surface mounting technology and printed circuits are passivated by top varnish for increased resistance. The input electric signal is converted by a 16-bite A/D convertor into the digital form. The instrument is calibrated by means of two-dimension polynomial
approximation of the third order. It is necessary to specify the type of analogue input in the order and it is not possible to change it subsequently. The display format, conversion constants and any other parameters are software adjusted by means of a configuration program which is started up under the operating system Windows. If the instrument is not equipped with a serial communication interface, it is necessary to use a special adaptor which is connected to the USB port of the computer. The 4-figure display can be highlighted by white LEDs in instruments which are not power supplied directly from the current loop. Highlighting is switched on either by an interconnector on the printed circuit or by the program. Sensors can also be equipped with a switching module equipped with a relay with one contact and two independent outputs type open collector with an NPN transistor with indication of switching by means of red LEDs, where the switching parameters are again adjustable only by the software. Another optional extension is a flash memory where the measured values with chosen time period can be stored and subsequently read through the serial interface.
The instruments are power supplied from a direct-current supply which can operate in a very wide range 5 to 36V. Change of the supply voltage in this range does not have any practical influence on the measuring accuracy. The instruments are protected against reversal of poles by a serial diode.
The two-conductor version 4-20mA can be power supplied directly from the measuring loop with a drop on the instrument max. 5V and it is protected against overload in the range of permitted supply voltage by an electronic current limiter. But this version is limited only for the function of a visual display unit without highlighting and additional outputs.
