MT-9004B page 1 of 2
MT90 Model
■
±1 RPM Accuracy
■
Easy Calibration
■
Clear-Read LCD Display
■
Back Light for Night Viewing
(Battery Powered models)
■
Input Source Can Be a Magnetic Pickup
or Engine Alternator
■
Power Supplied by Magnetic Pickup
or 12, 24, or 32 VDC Battery System
Description
The Murphy SELECTRONIC
®
MT90 is a digital
tachometer. Its high accuracy and dependability
result from use of a quartz crystal time based and
digital, solid-state electronics.
Tachometer power is supplied by either a Murphy
magnetic pickup, mounted at the flywheel ring-
gear of an engine, or by a 12, 24 or 32 volt DC
battery system.
RPM data is supplied by either a Murphy magnet-
ic pickup or by the alternator in your battery
charging circuit. The MT90 also has back-lighting
for easy readings in low lit areas; this lighting
requires a battery power source.
RPM Calibration
The MT90 is calibrated to engine RPM by setting a
series of calibration rotary switches on the back of
the tachometer. The proper switch sequence for the
engine is determined by (1) the number of ring gear
teeth for the magnetic pickup, or (2) by the ratio of
alternator to engine pulley diameter, and the num-
ber of poles of the alternator.
Applications
Typical applications include: Generators,
Compressors, Industrial Engines, Oil Field
Equipment, Marine Vessels, Vehicles, Farm
Equipment, and Construction Equipment.
Specifications
Signal Input Voltage:
4 to 35 Vrms from a mag-
netic pickup or alternator
**
.
Pulses per Revolution:
3 to 999.
Power Requirements:
•
Pickup Power:
4-35Vrms
**
.
•
Battery Power:
8-40 VDC (12, 24, 32 volt).
Current:
•
Tach back-light Off, 4mA @ 40 VDC.
•
Tach back-light On, 25 mA @ 40 VDC.
Case:
1018 polycarbonate/polyester blend.
Lens:
Polycarbonate.
Bezel:
#430 Stainless Steel.
Display:
LCD, 4-digit, seven segment.
Operating Temperature:
-4 to 158°F
(-20 to 70°C).
Storage Temperature:
-13 to 185°F (-25 to 85°C).
Mounting Hole:
3-7/16 in. (87 mm).
Shipping Weight:
14 oz. (0.4 kg).
Shipping Dimensions:
5-1/2 x 5-1/2 x 5-1/2 in.
(140 x 140 x 140 mm)
Warranty
A limited warranty on materials and workmanship is
given with this FW Murphy product. A copy of the
warranty may be viewed or printed by going to
www.fwmurphy.com/support/warranty.htm
*
Products covered by this bulletin comply with
EMC Council directive 89/336/EEC regarding
electro-magnetic compatibility except as noted.
**
See “Special Note” for Magnetic Pickup
Powered MT90 applications (back page).
Calibration
Rotary Switches
(located under
removable
rubber seal)
Mounting
Clamp
3-5/8 in
(92 mm)
3-1/8 in
(80 mm)
Terminal
Screws
0 1
2
3
6
9
45
7
8
0 1
2
3
6
9
45
7
8
0 1
2
3
6
9
45
7
8
X 1000
X 100
X 10
Dimensions
Side View
Back View
MT-9004B
Revised 03-06
Catalog Section 20
(00-02-0068)
Digital Tachometer by Murphy
SELECTRONIC
®
