What Is the NUS-7 Ultrasonic Level Transmitter?
The KOBOLD NUS-7 is a 2-wire ultrasonic level transmitter for liquids that measures level without contacting the medium, with the transducer and processing electronics built into one housing. It is designed for level measurement in sumps and tanks and for open channel flow, and comes standard with HART protocol.
The economical NUS-7 carries the echo detection features of the proven NUS-4 measurement systems in a compact 2-wire sensor housing. It provides a scalable 4-20 mA output and a programmable relay, and is suited for most liquids under various process conditions.
How the NUS-7 Measures Level
The NUS-7 emits an ultrasonic pulse train and receives the echoes reflected from the liquid surface. The intelligent electronics select the surface echo and calculate distance from the time of flight. A 4-20 mA signal is available for remote transfer and a relay contact for monitoring.
With a total beam angle of 5 degrees, the narrow, focused beam is designed to support reliable measurement in narrow silos with uneven walls and in process tanks with protruding objects, and to help the signal penetrate gases, vapor, and foam. Non-contacting measurement makes the transmitter well suited to applications where contact cannot be established, such as corrosive media like acids, contaminated media like sewage, or adhesive materials that cling to a probe.
NUS-7 Specifications and Performance
The NUS-7 measures liquids over a range of 0.8 to 20 feet (0.25 to 6 m) with an accuracy of ±(0.2% of reading + 0.05% of full scale) under optimal reflection and stabilized transducer temperature. Maximum process pressure is 40 PSIA and the housing carries an IP68 ingress protection rating.
Resolution depends on distance: 0.04 inch (1 mm) below 6.5 feet (2 m), 0.075 inch (2 mm) from 6.5 to 16.5 feet (2 to 5 m), and 0.2 inch (5 mm) above 16.5 feet (5 m). The ambient temperature range is -22 to 176°F (-30 to 80°C) and the process temperature range is -22 to 194°F (-30 to 90°C).
Materials and Process Connections
The NUS-7 housing and transducer are made of PP or PVDF, with EPDM cable sealing and PVC cable insulation. The process connection is 2 inch NPT or G 2. The integrated connection cable is a LIYCY 2 x 0.5 mm² (AWG 20) shielded type at a standard length of 16.5 feet (5 m), and can be ordered up to 100 feet (30 m).
Outputs, Communication, and Power
The 2-wire NUS-7 provides a standard 4-20 mA output with HART protocol into a maximum loop load of 600 ohms, plus a relay rated SPDT at 30 V / 1 A DC or 48 V / 0.5 A AC. It is powered by 12 to 36 VDC and draws 44 to 800 mW.
The HART interface reaches the full parameter set for configuration over the loop, and HART short addresses 0 to 15 identify units on the same loop. Linking a HART modem and PC lets one computer poll and reprogram a multi-drop group of as many as fifteen transmitters, which suits multiple-tank monitoring.
Measurement Functions and Applications
Beyond distance and level, the NUS-7 can be configured to output level percentage, volume, volume percentage, and open channel flow. Programmable features include measurement configuration, damping, target tracking speed, sound velocity correction, dome-top tank compensation, and 32-point linearization.
For volume, the transmitter offers 14 different tank contents profiles covering shapes such as standing cylindrical, conical-bottom, rectangular, lying cylindrical, and spherical tanks. For open channel flow, it offers 21 different profiles covering Parshall flumes, Palmer-Bowlus and Khafagi Venturi flumes, and weirs including V-notch, trapezoidal, Thomson, BAZIN, and circular types. Relay functions include differential level control, echo-loss indication, and a pulse counter for flow, while diagnostics include an echo map and a signal-to-noise ratio readout.
Installing the NUS-7
Mount the NUS-7 high enough that the maximum liquid level never enters the dead zone, the minimum measuring distance of 0.25 m (0.8 ft), since violating this block distance can lead to malfunction. The sensor face should sit parallel to the liquid surface within about 2 to 3 degrees.
Only one ultrasonic level device should be installed per container to prevent interference, and the transmitter should be protected from direct sunshine. Because foam can absorb ultrasonic signals and strong drafts can deflect them, choose a location away from the filling inflow where foaming and air movement are lowest, or use a stilling pipe or well.
Common Questions about NUS-7 - Ultrasonic Level Transmitter for Liquids
It sends ultrasonic pulses toward the liquid and times the echo returning from the surface, then converts that flight time into a distance and a level reading. The transducer and electronics sit in one housing, and a narrow 5 degree beam helps the pulse travel through vapor and foam.
The NUS-7 reads liquid levels from 0.8 to 20 feet (0.25 to 6 m). Its accuracy is ±(0.2% of reading + 0.05% of full scale) given good reflection and a settled transducer temperature. Resolution reaches 0.04 inch (1 mm) at distances shorter than 6.5 feet (2 m).
The NUS-7 offers PP or PVDF wetted parts for both housing and transducer. Maximum process pressure is 40 PSIA, and the process temperature range runs from -22 to 194°F (-30 to 90°C). It carries an IP68 rating and mounts with a 2 inch NPT or G 2 fitting.
Every NUS-7 ships with a scalable 4-20 mA loop carrying HART, together with a programmable relay. That relay switches SPDT loads up to 30 V / 1 A DC or 48 V / 0.5 A AC. Over HART you can read and set the complete parameter list from a connected PC.
The NUS-7 is a loop-powered 2-wire device that runs on 12 to 36 VDC, with power consumption between 44 and 800 mW and a maximum current-loop load of 600 ohms. The 2-wire design is intended for DC-powered applications and for low switching capability.
Yes. With a HART modem and a PC, up to 15 NUS-7 transmitters can share one multi-drop loop, and the computer can display and reprogram each of them. Short HART addresses 0 to 15 tell the units apart on the shared line.
Yes. Besides level, the NUS-7 reports tank volume and percent full from 14 built-in vessel-shape profiles. For flowing water it supports 21 open channel profiles for flumes and weirs, and it can pulse a relay to help totalize flow.
Build the code from housing material (0 = PP, 9 = PVDF), range (06 = 0.8 to 20 feet), connection (N9 = 2 inch NPT, R9 = G 2), power (3 = 12 to 36 VDC), output (4H = 4-20 mA plus HART, RH also adds a relay), and cable length (5 = 16.5 feet, EC = custom to 100 feet). Example: NUS-7 0 06 R9 3 4H 5.
Position the transmitter so the highest liquid never rises into the 0.25 m (0.8 ft) blocked dead zone, and align the sensor face to within a few degrees of the surface. Use one ultrasonic unit per tank, shield it from direct sunshine, and steer clear of foam and heavy drafts.