APG MNU Installation Guide
APG
Thank You
Thanks for purchasing a MNU ultrasonic Modbus sensor from us! We appreciate your business and
your trust. Please take a moment to familiarize yourself with the product and this manual before
installation. If you have any questions, at any time, don’t hesitate to call us at 888-525-7300.
NOTE: Scan the QR code to the right to see the
full user manual on your tablet or smartphone. Or
visit www.apgsensors.com/support to nd it on our
website.
MNU Ultrasonic Modbus Sensor
Installation Guide
Table of Contents
1.Description
2. How To Read Your Label
3. Warranty
4. Mounting Instructions
Description
1
MNU ultrasonic sensors are rugged units, with a PC/PBT housing, 1”-3” NPT threads for mounting,
and a NEMA 6P rating (protects against ingress of dripping, sprayed, and submersing water). All
MNU sensors are fully programmable via RST-485 Modbus communications with APG Modbus
software and an APG RST-6001 unit.
How To Read Your Label
2
Each label comes with a full model number, a part number, and a serial number. The model
number for the MNU will look something like this:
SAMPLE: MNU-3434-M
5. Dimensions
6. Wiring Information
7. General Care
8. Repair Information
9. Removal Instructions
R
Automation Products Group, Inc.
1025 W 1700 N Logan, UT 84321
www.apgsensors.com | phone: 888-525-7300 | email: sales@apgsensors.com
Dimensions
5
7.21”
3/4” ø NPT
2” ø NPT
Threads
Threads
129.03mm
3.05”
77.47mm
1.47”
37.34mm
183.13mm
5.08”
3” ø NPT
Threads
3/4” ø NPT
Threads
Part # 122950-0010
Doc #9004244 Rev C
2.27”
57.66mm
5.63”
143.00mm
2.80”
71.12mm
7.76”
197.10mm
The model number correlates with all the congurable options and tells you exactly what you have.
Compare the model number to the options on the datasheet to identify your exact conguration.
You can also call us with the model, part, or the serial number and we can help you.
The label also includes the pinout, as does this installation guide.
Warranty
3
This product is covered by APG’s warranty to be free from defects in material and workmanship
under normal use and service of the product for 24 months. For a full explanation of our Warranty,
please visit https://www.apgsensors.com/about-us/terms-conditions. Contact Technical Support to
receive a Return Material Authorization before shipping your product back.
Scan the QR code below to read the full explanation of our Warranty on your tablet or smartphone.
1.98”
50.29mm
MNU-2424 & MNU-8424
3/4” ø NPT
Threads
3.97”
100.84mm
2.73”
1” ø NPT
Threads
63.34mm
0.68”
17.27mm
6.10”
154.94mm
3/4” ø NPT
2” ø NPT
Threads
Threads
3.00”
76.20mm
MNU-3434
77.47mm
3.05”
145.80mm
3.61”
91.69mm
5.74”
Mounting Instructions
4
Mounting your MNU ultrasonic sensor is easy if you follow a few simple steps:
• Never over-tighten the sensor.
• Always screw in your sensor by hand to avoid cross-threading. Thread failure can be a
problem if you damage threads by over-tightening them or by crossing threads.
• Mount your MNU sensor so that it has a clear, perpendicular sound path to the surface being
monitored. Your sensor should be mounted away from tank or vessel walls and inlets. (See
Figure 4.1)
• The sound path should be free from obstructions and as open as possible for the 9° o axis
beam pattern.
• If you are using a stand pipe, please see our guide to stand pipes on our website:
http://www.apgsensors.com/about-us/blog/how-to-install-a-stand-pipe.
MNU-5424MNU -5 414
Figure 4.1
Wiring Information
6
Modbus
Red + 24 VDC
Power Supply 12-24 VDC
Modbus
Black DC Ground
Pigtail
Green B (TX-)
White A (TX+)
(2 Twisted Pairs)
Shield Case Gnd
1 Brown +24 VDC
2 White A (TX+)
Micro
Connector
3 Blue DC Ground
4 Black B (TX-)
IMPORTANT: Some modbus equipment uses reversed TX+/TX- pins. When making
connections between APG equipment, ensure A to A and B to B connections. When
connecting to other systems, if your MNU sensor will not communicate, reverse A & B
connections at one end (Master OR Sensor, not both).
Connection to
network/Internet
RST-5003
Modbus
Equivalent 270 Ω
terminating resistor
internal to RST-5003
+12-24 VDC / GND
Power Supply
Controller
Modbus
Connection
Use Shielded Cable
MNU sensor MNU sensor MNU sensor
Sensor 1
V+ / GND
A & B
Sensor 2
V+ / GND
A & B
MNU Modbus System Wiring with RST-5003
and Power Supply
Sensor 3
V+ / GND
A & B
270 Ω terminating
resistor at last sensor
across A & B terminals
Power
Supply
RST-6001
Controller
Modbus
+8-24 Vdc
GND
RS-485 A (TX+)
RS-485 B (TX-)
+12-24 Vdc
Power
Supply
Master
Device
Note: Some modbus equipment
uses reversed TX+/TX- pins. When
making connections between APG
equipment, ensure A to A and B to B
connections.
USB to computer
with APG Modbus
software
Note: An independent +12-24 Vdc
power supply is required when using
an RST-6001 Modbus Controller. The
RST-6001 can only supply ±5 Vdc, not
the +12-24 Vdc required by the MNU.
Use Shielded Cable
120 Ω
terminating
resistor
MNU Sensor MNU Sensor MNU Sensor
Sensor 1
V+
B (TX-)
A (TX+)
GND
B (TX-)
A (TX+)
MNU Modbus System Wiring
MNU sensor
Sensor 1
V+
B
A
GND
Use Shielded Cable
GND
A
B
-5V
+5V
Equivalent 120 Ω
terminating resistor
internal to RST-6001
Sensor 2
V+
GND
MNU sensor MNU sensor
Sensor 2
V+
B
A
GND
Sensor 3
V+
B (TX-)
A (TX+)
GND
Sensor 3
GND
120 Ω terminating
resistor at last sensor
V+
B
A
120 Ω terminating
resistor at last sensor
Connection to
network/Internet
Equivalent 270 Ω
terminating resistor
internal to RST-5003
RST-5003
Controller
Modbus
Connection
+VDC
Modbus
GND
MNU sensor MNU sensor MNU sensor
Sensor 1
V+ / GND
A & B
Power must be supplied to RST-5003 via POE
(Power Over Ethernet) or 24VDC daisy-chain at
+VDC / GND terminals
Use Shielded Cable
Sensor 2
V+ / GND
A & B
Sensor 3
V+ / GND
A & B
270 Ω terminating
resistor at last sensor
across A & B terminals
MNU Modbus System Wiring with RST-5003
and Power Over Ethernet (POE) or VDC
MNU Modbus System Wiring with RST-6001
General Care
7
Your MNU ultrasonic sensor is very low maintenance and will need little care as long as it was
installed correctly. However, in general, you should:
• Avoid applications for which the sensor was not designed, such as extreme temperatures,
contact with incompatible corrosive chemicals and fumes, or other damaging environments.
• Inspect the threads whenever you remove the sensor from duty or change its location.
NOTE: See your MNU User Manual for Modbus programming
instructions and troubleshooting tips.
Repair Information
8
If your MNU sensor needs repair, contact us via email, phone, or on-line chat on our website. We
will issue you an RMA number with instructions.
• Phone: 888-525-7300
• Email: sales@apgsensors.com
• Online chat at www.apgsensors.com
Removal Instructions
9
• Ensure that power to the sensor is o
• Disconnect cable to sensor.
• Remove the sensor and store it in a dry place, at a temperature between -30° F and 140° F.
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