Bently Nevada 991-05-70-01-01 Thrust Transmitter

Configured for continuous axial shaft position measurement in rotating machinery protection systems, the Bently Nevada 991-05-70-01-01 (991 Thrust Transmitter) provides direct conversion of proximity probe displacement signals into a proportional 4-20 mA output. The transmitter operates with Bently Nevada 3300 NSv proximity probe systems and delivers continuous thrust position monitoring for integration with PLC, DCS, recorder, and protection system inputs.

Suffix Breakdown & Model Matrix

The supplied documentation identifies the following configuration elements within the 991-05-70-01-01 ordering structure.

• 991 designates the Thrust Transmitter product family.

• 05 specifies a current loop measurement range of 0.6-0-0.6 mm (25-0-25 mils).

• 70 identifies a 7.0 m total transducer system length.

• 01 specifies the 35 mm DIN rail mounting option.

• 01 identifies the approved agency-certified version for this configuration.

Only suffix definitions explicitly provided in the supplied documentation are included above.

Hardware Specifications

Eddy-Current Probe Scaling and Gap Voltage Validation

The 991 transmitter utilizes eddy-current proximity measurement technology to monitor axial shaft position relative to the machine casing. Proper operation depends on compatibility between the transmitter, 3300 NSv probe, and specified 7.0 m transducer system length. During commissioning, gap voltage verification is commonly performed to confirm operation within the calibrated linear measurement region. For proximity measurement systems, nominal operating targets near -10 VDC are frequently used to validate probe positioning, transducer scaling, and thrust measurement linearity before placing the machine into service.

Frequently Asked Questions

Q: What happens when a Not OK condition occurs?
A: The transmitter forces the output current below 3.6 mA within 100 us after a fault condition is detected. Normal output operation resumes within 0.1 seconds after the condition clears.

Q: Which probe system is supported by the 991-05-70-01-01?
A: The transmitter is designed for operation with a Bently Nevada 3300 NSv proximity probe system.

Q: What is the maximum loop resistance supported by the transmitter?
A: The specified maximum loop resistance is 1000 Ohm, including cable resistance, when operating from a 35 VDC supply.

Field Installation Guidelines

• Verify compatibility between the transmitter, probe, and extension cable before installation.

• Confirm that the complete transducer system length matches the specified 7.0 m configuration.

• Install the transmitter on a secure 35 mm DIN rail inside a grounded enclosure.

• Route proximity probe wiring separately from motor power cables and high-energy switching circuits.

• Maintain cable shield continuity according to site instrumentation standards.

• Validate probe gap voltage prior to commissioning thrust measurement channels.

• Confirm loop supply voltage remains within the specified 12 VDC to 35 VDC operating range.

• Verify 4-20 mA scaling at the receiving control or monitoring system before placing equipment into operation.