4-20 mA Installation

Operation & Maintenance Manual

4-20 mA VIBRATION TRANSMITTER Model 125 & 12                                                                 

Caution:This guide should be read carefully before installation.

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INTRODUCTION

Loop-powered, 4-20 mA output, vibration sensing transmitters serve to provide measurement signals that are representative of the overall vibration levels being generated by all types of rotating machinery. This vibration signal may be interfaced with many types of current-loop monitoring equipment, such as recorders, alarms, PLC, DCS, and SCADA systems. The purpose of the 4-20 mA analog current loop is to transmit the signal from an analog vibration sensor over a distance in the form of a current signal. Loop power accelerometers output a current : 4 mA normally representing the sensor’s zero-level output, and 20 mA representing the sensor’s full-scale output. A choice of velocity or acceleration measurement signals are offered with a variety of amplitude and frequency ranges to suit the particular application. All models feature an optional analog output signal connection (DV or DA option) for conducting frequency analysis and machinery diagnostics Only two wires are required to send the current signal and also supply power to the sensor. A series resistor R at the loop power supply converts this current to a voltage that can be used by the process monitor/ controller to record or distribute the parameter being measured.

GENERAL FEATURES

• Embedded Piezoelectric Accelerometer for Improved accuracy and frequency response.
• Vibration range can be Acceleration or Velocity.
• Allows for continuous vibration monitoring of critical applications.
• Reduces sophisticated vibration analysis requirements.
• DV/DA (Raw Vibration) option for conducting frequency analysis and machinery diagnostics.
• Readily interfaces to existing process control and predictive maintenance equipment.
• Rugged stainless steel construction for applications in harsh environments.
• flexible design a1lows for various custom requirements.

SPECIFICATIONS & ORDERING INFORMATION

See datasheet 125
See datasheet 127 

4-20 mA INSTALLATION WITH DYNAMIC OUTPUT OPTION (DA or DV option) : 4-20 MA INPUT CARD

Attach positive (+) input from the power supply to Pin +, onto the sensor, and the negative (-) input from the power supply to Pin - of the sensor.
Datasheet gives color of wires for Pin + , Pin - and Dynamic Output.
Wiring colors for standard M12 cable assembly : (4-20mA +) Brown // (4-20 mA -) White // (DA or DV) Black // (Not connected) Blue

 


4-20 mA INSTALLATION WITH DYNAMIC OUTPUT OPTION (DA or DV option) : 0-10 VDC INPUT CARD

Attach positive (+) input from the power supply to Pin +, onto the sensor, and the negative (-) input from the power supply to a load resistor (R) in line with the Pin - of the sensor.
Datasheet gives color of wires for Pin + , Pin - and Dynamic Output.

The resistor R will generate a DC voltage that is proportional to current by: U = R . I
Example : R=500 Ohms and I=6mA, then U=3 VDC

4-20 mA INSTALLATION WITH TEMPERATURE OUTPUT (T0 Option): 4-20 MA INPUT CARD 

The T0 option includes a temperature output (10 mV/°C) The temperature output requires 2 wires therefore you cannot have both dynamic output and temperature output.
Wiring colors for standard M12 cable assembly : (4-20mA +) Brown // (4-20 mA -) White // (Temp +) Black // (Temp -) Blue

4-20 mA MAXIMUM LOOP RESISTANCE

Maximum loop resistance R can be calculated by R (max resistance) = (Vsupply - 10V)*1000 / 20 mA 

DC supply voltage	R (max resistance) (1)	R (Minimum wattage capability) (2)
12 VDC	10 Ω	1/8 watt
24 VDC	700 Ω	1/2 watt
30 VDC	1.0 kiloΩ	1/2 watt

1. Lower resistance is allowed, greater than 10 O recommended.
2. Minimum R wattage determined by: (0.0004 x R)

4-20 mA MAXIMUM CABLE LENGTH

With R=250 Ohms and 24 VDC supply the maximum distance could be as high as 15 000 metres.

DYNAMIC OUTPUT (DA or DV option)

The DA (raw acceleration) option includes a 100 mV/g additional output.
The DV (raw velocity) option includes a 100 mV/ips additional output .
The accelerometer frequency range (DA) is 0.5 Hz-10kHz with maximum amplitude of 25 g-pk.
The common for the dynamic output is also the return signal for the 4-20 mA loop wiring.Connecting this pin to ‘ground’ will usually short out the 4-20 mA loop return resulting in a loss of the 4-20 mA signal. The dynamic output is designed to be used by portable data collectors where no direct connection to ground exists. It can also be used by on-line systems when their signal input is galvanically isolated from ground.

LOOP RESISTANCE CALCULATION

To operate, make sure that all wires are properly connected, then apply power.
When reading the current output, use the following table for expected output.

  

Example :    

Sensor with Full Scale = 20 mm/s RMS Sensor with Full Scale = 10    g RMS

Measured Vibration 4 mA 0 mm/s RMS 8 mA 5 mm/s RMS 12 mA 10 mm/s RMS 16 mA 15 mm/s RMS 20 mA 20 mm/s RMS

Measured Vibration 4 mA 0 g RMS 8 mA 2.5 g RMS 12 mA 5 g RMS 16 mA 7.5 g RMS 20 mA 10 g RMS

Caution

Power input should not exceed specified limits or damage may result.
Power input (+) should not be wired to Dynamic output or damage may result.

MAINTENANCE

There are no customer replaceable parts. The amplifier has been designed for trouble-free service under normal operating conditions. VibraSens warrants the equipment for 2 years. If your instrument require repair, you may contact our customer service representative at:

support@vibrasens.com