Configured for radial vibration measurements in machinery protection applications, the Bently Nevada 990-05-70-01-CN (990 Vibration Transmitter) provides direct physical/electrical execution.

Suffix Nomenclature Breakdown

The modular options for the 990-05-70-01-CN transmitter are designated as follows:

• 990: Base model series for the Bently Nevada non-contacting vibration transmitter.

• -05: Full-scale range option of 0-5 mils peak-to-peak (0-125 micrometers peak-to-peak).

• -70: System length option calibrated for a 7.0 m (23.0 ft) combined probe and extension cable configuration.

• -01: Integrated 35 mm DIN rail mounting clips.

• -CN: Hazardous area agency approvals including CSA Class I, Division 2, ATEX Zone 0/Zone 2, and ABS maritime certification.

Hardware Specifications

Eddy-Current Probe Scaling and Loop Tuning

The 990-05-70-01-CN transmitter combines Proximitor sensor electronics and a signal conditioner into a single unit. It performs high-frequency eddy-current probe scaling when paired with a compatible 3300NSv proximity probe. By exciting the probe coil, the transmitter senses changes in loop impedance as the shaft moves, converting this physical gap variation into a continuous 4-20 mA current loop.

To maintain calibration accuracy, gap voltage validation must be performed during mechanical setup. The target gap voltage of -10 VDC at the coaxial terminal ensures the 3300NSv probe sits in the middle of its linear range. Proper calibration isolates the signal from adjacent machinery vibration and preserves the 10 kHz signal resolution.

Ordering Info

• 1 x Bently Nevada 990-05-70-01-CN Vibration Transmitter

• 1 x Set of pre-installed 35 mm DIN rail mounting clips

• 1 x Hardcopy installation sheet

Shielding and Grounding Standards

• Common Mode Ground Isolation

  The transmitter chassis is electrically isolated from the internal electronics. Ensure that terminal 3 (shield/common) is grounded at a single point, typically at the DCS or safety barrier, to prevent ground loop currents.

• Dynamic Terminal Protection

  The coaxial BNC output provides raw dynamic voltage signals for diagnostic tools. When not connected to an analyzer, keep the BNC terminal covered with a protective dust cap to prevent moisture ingress.

• DIN Rail Mechanical Stability

  Ensure the 35 mm DIN rail is rigidly anchored to the backplate inside the enclosure. High ambient machine vibration can cause mechanical wear at the mounting clips if the rail is loose.

Frequently Asked Questions

• What target gap voltage is required to center this transmitter within its linear range?

  The physical probe must be adjusted until the DC gap voltage at the dynamic output terminal measures -10 VDC.

• Can this transmitter be hot-swapped while the loop is powered?

  Yes, but removing the unit breaks the 4-20 mA loop, which will register as a fault at the control system. Ensure the channel is bypassed first.

• What is the maximum distance allowed for the 4-20 mA loop wiring?

  The loop length is limited by loop resistance; with a 24 VDC supply, it supports up to 500 ohms of total wire resistance.

• Does this transmitter accept standard 3300 XL 8 mm proximity probes?

  No, the 990 series transmitter is strictly calibrated to interface with 3300NSv probes and extension cables.

• How is the dynamic vibration signal accessed for offline diagnostics?

  A portable data collector or oscilloscope can be connected directly to the coaxial BNC terminal on the front face.

• What happens if a 5.0-meter cable is used instead of the 7.0-meter option?

  The transmitter is factory-calibrated for a 7.0-meter system; a mismatch will alter the scaling factor and degrade measurement accuracy.

• Is an external safety barrier required for ATEX Zone 0 installation?

  Yes, an intrinsically safe zener barrier or galvanic isolator must be installed in the loop wiring for hazardous areas.

• What is the behavior of the loop current if the probe cable is severed?

  The loop current will drop below 3.6 mA, signaling a "Not OK" or sensor fault condition to the DCS.