CEMB TR-NC/8 Relative Vibration and Axial Displacement Transmitter

The CEMB TR-NC/8 is a two-wire 4-20 mA transmitter for monitoring the relative vibration or the axial position of a rotating shaft. It works as part of a proximity measuring chain, an ST-NC/8 eddy-current probe and an extension cable, and its current signal goes directly to a PLC or DCS. That makes it a compact way to add shaft vibration and thrust position protection to turbines, compressors, gearboxes and other plain-bearing machines without a rack-mounted monitor.

Technical specifications

Matching the transmitter, probe and cable

A proximity chain is calibrated as a set, so the probe, cable and transmitter must be specified together. The order code TR-NC/8/A/B/C/D/E defines the measurement type, chain length, range, target material and certification. The target material matters because the eddy-current sensitivity depends on the shaft steel; state the shaft grade when ordering instead of accepting the AISI 4140 default. The gap voltage test contacts allow the probe to be set to the middle of its linear range during installation, which is the step that most often decides whether the reading is correct.

Choosing it for a machine

Choose measurement type 1 for relative shaft vibration across a plain bearing and type 2 for axial position or thrust bearing wear, with a separate chain for each point. For hazardous areas select certification code 2 or 3; the intrinsically safe ATEX version has narrower ambient limits for the transmitter, as shown in the table, and requires an approved barrier or isolator in the safe area. For housing-mounted absolute vibration see the CEMB TR-26 vibration transmitter or the CEMB TR-PRO high performance vibration transmitter; the full range is listed under vibration monitoring.

How the CEMB TR-NC/8 works

The probe tip makes a high frequency field and an eddy current in the shaft. When the gap between the tip and the shaft changes, the field changes too. The transmitter turns this change into a current between 4 and 20 mA. A steady gap moves the signal to a set level, and a vibration adds a small moving part to it.

Where the TR-NC/8 is used

• Steam and gas turbines
• Compressors
• Gearboxes
• Plain-bearing pumps
• Machines that need axial position protection

Selection checklist for the TR-NC/8

• Vibration or axial displacement
• Measuring range
• Target material
• Chain length of 5, 7 or 9 m
• Probe thread and body length
• Extension cable length
• Armoured cable need
• Certification code

Installation, commissioning and maintenance notes for the TR-NC/8

Fit the probe in its holder at the right gap from the shaft. Join the probe, the extension cable and the transmitter as one set. Clip the transmitter on a DIN rail and connect the 24 V DC supply. Read the gap voltage on the check contacts and adjust it. Keep the cable connectors clean and dry.

Requesting a quotation for the CEMB TR-NC/8

Please send the measuring range, the target material and the chain length. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

TR-NC/8 measuring chain

The chain has the transmitter, the ST-NC/8 probe and an extension cable.

TR-NC/8 output signal

The output is a 4 to 20 mA current loop on two wires.

TR-NC/8 supply voltage

The supply is 24 V DC, with a range of 18 to 32 V DC.

TR-NC/8 vibration range

Vibration ranges run from 0-100 to 0-250 micrometre peak to peak.

TR-NC/8 axial displacement range

Axial displacement ranges are plus or minus 0.5, 0.75 or 1 mm.

TR-NC/8 frequency response

Vibration response covers 1.5 Hz to 10 kHz.

TR-NC/8 linearity

The linearity is plus or minus 2 percent.

TR-NC/8 target materials

The default target is AISI 4140, and other steels can be chosen in the code.

TR-NC/8 connectors

A BNC socket allows a portable analyser to be connected.

TR-NC/8 temperature range

The transmitter works from minus 40 to plus 80 degrees C.

TR-NC/8 probe adapter

The SR-6 adapter helps with rotor-side installation and field setting.

Sensor records for the TR-NC/8

Record the gap voltage, the chain length and the date of each check.

Choosing the right TR-NC/8 chain

Match the range to the expected shaft motion and the chain length to the cable route.

Documents and quotation

The linked document is the CEMB TR-NC/8 data sheet, which includes the ordering codes for the transmitter, probe and extension cable. Before ordering confirm the shaft material, measuring range, chain and cable lengths, probe thread and body length, and the certification required. Seven Star LLC, an independent supplier in Muscat, will quote from the complete codes.