The 991 Thrust Transmitter is intended primarily for the original equipment manufacturers (OEMs) of centrifugal air compressors or small pumps, motors, or fans who prefer to provide a simple 4 to 20 mA proportional axial displacement (thrust) signal as the input to their machinery control system.

The transmitter is a 2-wire, loop-powered device that accepts input from our 3300 NSv* proximity probe and its matching extension cable (available in 5 m and 7 m system length options). The transmitter conditions the signal into appropriate engineering units proportional to the shaft’s axial position¹, and provides it as a 4 to 20 mA industry-standard signal for input to the control system where machinery protection alarming and logic occurs².

The 991 transmitter provides the following notable features:

• Integrated Proximitor* Sensor requires no external unit
• Non-isolated “PROX OUT " and "COM" terminals plus a coaxial connector provide a dynamic vibration and gap voltage signal output for diagnostics³.
• Non-interacting zero and span potentiometers under the Transmitter label supports loop adjustment.
• Test Input pin allows quick verification of loop signal output, using a variable DC voltage source as the input.
• A Power-up Inhibit circuit eliminates signal errors due to line voltage transients.
• A Not OK/Signal Defeat circuit prevents high outputs or false alarms due to a faulty proximity probe or loose connection.
• Choice of DIN-rail clips or bulkhead mounting screws as standard options simplifies mounting.
• Potted construction for high humidity (up to 100% condensing) environments.
• Compatibility with 3300 NSv proximity probe allows transducer installation in small areas with minimal clearance, typical of centrifugal air compressors

Parameter	Value
Manufacturer	Bently Nevada
Product Category	TSI System
Estimated shipping dimensions	10x7.3x6cm
Weight	1.0 kg
Tariff Code	8537101190
Country of origin	USA
Place of shipment	Shenzhen,China
Full-scale Option	0.6-0-0.6 mm
System Length	7.0 meters (23.0 feet)
Mounting Option	35 mm DIN-rail clips
Product Type	991 Thrust Transmitter
Measurement Type	Axial displacement (thrust)
Power Supply	2-wire, loop-powered device
Maximum Loop Resistance	1,000 Ω including cable at 35 Vdc
Current Limiting	23 mA typical

 

991-06-70-01-05 is a thrust transmitter from the 991 series. This device is specifically designed for axial position monitoring in industrial rotating machinery applications.

The measurement parameters of 991-06-70-01-05 are configured with a full-scale option of 0.6-0-0.6 mm, providing bidirectional thrust displacement monitoring centered around zero position. The system incorporates a total length of 7.0 meters (23.0 feet), accommodating extended installation distances between the sensing point and monitoring equipment.

Regarding mechanical installation, 991-06-70-01-05 utilizes 35 mm DIN-rail clips as the mounting option, enabling convenient and standardized mounting within industrial control panels and electrical enclosures. This mounting configuration facilitates quick installation and easy maintenance access.

991-06-70-01-05 holds comprehensive agency approvals including CSA Division 2, ATEX Zone 0, and ATEX Zone 2 certifications, ensuring safe operation across various hazardous location classifications from continuously explosive atmospheres to unlikely explosive conditions. Additionally, this transmitter includes ABS maritime approval, certifying its suitability for marine and offshore applications.

Specifications 

Unless otherwise noted, the following specifications

apply at +22 C (+72 F) using a 3300 NSv Probe and

Extension Cable, and an AISI 4140 steel target.

Electrical

Input

Accepts 1 non-contacting 3300 NSv

Proximity Probe and extension cable.

Power

Requires +12 to +35 Vdc input at the

transmitter terminal.

4 to 20 mA Signal

Output

4 to 20 mAdc over specified full-scale

range in 2-wire configuration.

4 to 20 mA Loop

Accuracy

Within ±1.5% over specified full scale

range (typical). Accuracy is rated

from the TEST signal input to the

voltage measured across a 250 

loop resistance.

Maximum Loop

Resistance

1,000  including cable at 35 Vdc.

Current Limiting

23 mA typical.

Zero and Span

Non-interacting external

adjustments.

Not OK/Signal

Defeat

Signal output will go to less than 3.6

mA within 100 µs after a Not OK

condition occurs. Signal output is

restored within 0.1 seconds after the

Not OK condition is removed.

Proximitor Sensor

Output

Compatible with ungrounded,

portable test equipment. When using

grounded, ac-powered test

equipment, use the 122115-01 Test

Adapter for signal isolation.

Output Impedance

Prox Out has a 10 k output

impedance calibrated for a 10 M

load.

Linear Range

0.25 to 1.65 mm (10 to 65 mils) for

Prox Out. Suitable for 0.6-0-0.6 mm

or 25-0-25 mils current loop linear

ranges.

Prox Out

Incremental Scale

Factor

7.87 mV/µm (200 mV/mil) ± 6.5%

typical including interchangeability

errors when measured in increments

of 0.25 mm (10 mils) over the linear

range using a flat 30 mm (1.2 inch)

target.

Temperature

Stability

Incremental scale factor remains

within ±10% of 7.87 mV/µm (200

mV/mil) from 0 C to +70 C (+32 F to

+158 F).

Minimum target

size

9.5 mm (0.375 in) diameter.

Leadwire Length

Proximitor* Sensor Output (BNC

connector), maximum cable distance

is 3 metres (10 feet).

Non-Hazardous,

Zone 2 or Div 2

Hazardous area

locations

13 km (8 miles) maximum between

transmitter and receiving device for

signal output.