Non-contact tachometer DT920

panel-mountwith LCD displayintrinsically safe

Product features

• NAMUR, switching transistor, contact inputs
• 4 limit outputs
• 4-20 mA scalable analog output
• The following parameters can be set: teeth number, transmission ratio, limit values, 4-20 mA scale
• Large (25 mm) LCD
• Intrinsically safe, usable in potentially explosive environment
• IP65 protection

Product description
The DT920 Intrinsically Safe Tachometer enable the revolutions per minute (RPM) of a shaft of a spin-dryer, of a stirrer etc. to be displayed in even the most hazardous plant areas (zone 1, 2). Various kinds of two wire sensors (magnetic, optical, with NAMUR, transistor, contact output) are possible to connect to the input of the instrument.
The DT920 receive the impulses generated by the sensor, the parameters, that is: the number of teeth of the dial, the transmission ratio can be set by using the front panel membrane keypad.
The instrument have four optically isolated transistor outputs for limit signalling or for simple control purposes.
The DT920 optionally may be equipped with a 4-20 mA transmitter output. The output is scalable: the 20 mA value can be assigned to any RPM values. The output can be used either for signal processing, or for the operation a secondary display.
The DT920 is housed in a moulded polycarbonate case which is dust-tight and houseproof to IP65 to, allow for installation in the field or on the control panel.
Large 4 digit, 25 mm height liquid crystal display make RPM value easily visible at a distance.

Technical specifications
Safety data: The connection terminals of the supply voltages are isolated from each other, the isolation is in compliance with the standard
EN 61010-1, taking into consideration the following:

• Pollution level: 2
• Measurement category: II

Intrinsical safety data:

• Certification: BKI 15 ATEX 0036 X
• Protection marking: II 2G Ex ia IIC T4 Gb (-20 °C < Ta < +60 °C)

Input parameters:

• Digital inputs:
• Input: for the connection of NAMUR (DIN 19234) / contact / switching transistor
• No-load voltage / inner resistance: 8.2 V / 1 kohm
• Frequency range: 0.3-5000 Hz

Output parameters:
Analogue output:

• Output signal: DC current
• Range: 4-20 mA
• Overdrive: 10%
• Overvoltage protection: 8.6 V (limiter)
• Overcurrent protection: 50 mA (limiter)
• Error of the output signal: 0.5% (max.)
• Temperature-coefficient: 50 ppm / OC (typically)
• Supply-voltage effect: practically zero
• Loading-effect: practically zero

Digital outputs:

• Output: 4 passive switching transistor
• Load rating: 30 V, 35 mA, 200 mW

Display / manual controls:

• Display: 4 digit LCD, 7 segments, decimal point
• Display unit: 25 mm character height
• Display range: 0.000-9999
• Accuracy: ±1 digit
• Indicators: 4 LED for limit values
• Manual controls: 4 push-buttons on the front cover

Power supply:

• Supply voltage: 18 VDC (intrinsically safe)
• Supply current: 70 mA
• Consumption: 1.4 W (max.)

Ambient conditions:

• Operating temperature range: -20 - +60°C
• Relative humidity: 90% (max., non-condensing)
• Place of installation: potentially explosive area

Electromagnetic compatibility (EMC) accordance with the standard EN 61326-1

• Immunity: industrial area
• Noise emission: Group 1, Class B

General data:

• Housing: moulded polycarbonate case; installable as a field or panelinstrument
• Connection: IP65 cable entry, screw terminal
• Connection cable: 0.25-1.5 mm2
• Dimensions / weight: 167 × 87 × 95 mm (width × height × depth) / 0.8 kg
• Protection: IP65

Detailed information see in operating instructions. The Manufacturer maintans the right to change the technical data!