
Instruction Manual
Single-Input Thermistor
Thermometer
(Model 91428-05)
68X001349 Rev0 0717 1065DGMAN_91428-05

99 Washington Street
Melrose, MA 02176
Phone 781-665-1400
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com

TABLE OF CONTENTS
1. QUICK-START GUIDE ........................... 1
2. INTRODUCTION .................................... 2
3. SAFETY PRECAUTIONS ....................... 3
4. SPECIFICATIONS ................................. 4
5. BATTERY INSTALLATION AND
REPLACEMENT .................................... 5
6. INSERTING AND REMOVING
OPTIONAL RUBBER ARMOR ............... 6
7. ASSEMBLING OPTIONAL HANDS-
FREE ACCESORIES ............................. 7
8. CONNECTING A THERMISTOR............ 8
9. KEY FUNCTIONS .................................. 9
10. DISPLAY OVERVIEW ...........................10
11. MEASUREMENT MODE .......................11
12. SELECTING TEMPERATURE SCALE ..12
13. MIN AND MAX FUNCTION ...................12
14. AUTO OFF FUNCTION .........................13
15. CALIBRATION ......................................13
16. CLEAR FIELD CALIBRATION ...............14
17. FIELD CALIBRATION UNLOCK ............15
18. FIELD CALIBRATION LOCKOUT .........16
19. MAINTENANCE ....................................17
20. CLEANING ............................................17
21. BATTERIES ..........................................17
22. TROUBLESHOOTING ..........................18
23. ACCESSORIES ....................................19
24. WARRANTY .........................................20
25. PRODUCT RETURN .............................20
26. INNOCAL® CALIBRATION AND REPAIR
SERVICES (NORTH AMERICA) ..........21

1. QUICK-START GUIDE
To ensure best results please read the
complete manual.
1. Connect probe.
2. Press the on/off key.
Press again to turn on backlight.
3. Select °C or °F display using °C/°F key.
4. Insert probe in sample.
Allow adequate time for reading to
stabilize.
Response time will vary depending on
probe.
5. Take reading.
Press hold key to freeze display.
Press min/max to display minimum or
maximum temperature.
6. Press and hold the on/off key for three
seconds to turn meter off.
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2. INTRODUCTION
Thank you for choosing the
Single-Input Thermistor
Thermometer. This sturdy
handheld thermometer
provides highly accurate
temperature measurements
using thermistor probes. The
instrument is easy to use and
includes the following
features:
• Operator selection of Celsius or Fahrenheit
scale
• Resolution of 0.1° C/F
• Large backlit LCD with two lines of
four-digit display
• Hold feature for temporarily retaining
a reading
• Min and max readings display
•
Field calibration capability
•
Auto power off with Enable/Disable function
• Low-battery warning
• Standard ¼ inch (6.3mm) phone jack
connector input
• Operates with a wide selection of probes
- 2 -

3. SAFETY PRECAUTIONS
Voltages present at the thermistors may
also be present at the battery terminals.
Always disconnect the thermistor when
changing batteries.
This instrument is designed to accept low
level signals supplied by standard 400
series thermistors. Under no
circumstances should the input voltage
exceed the specified 10 v rms.
1. Do not use or store this instrument in
microwave ovens or any abnormally hot or
cold areas.
2. Weak batteries should not be left in the
instrument. Dead batteries can leak and
cause damage to unit.
- 3 -

4. SPECIFICATIONS
–40 to 150°C
(–40.0 to 302.0°F)
±0.2°C (±0.4°F) from
–40 to 125°C (-40 to 257°F)
±0.5°C (±0.9°F) from
125 to 150°C (257 to 302°F)
4+4 digit, 58 x 40mm dual-line
display with backlight
One probe with ¼ inch (6.3mm)
phone jack connector
700 hours continuous, typical
17 minutes after last key press
“STABLE” will display upon
5 seconds of stability
–40 to 65°C (–40 to 149°F)
10% to 90% RH (noncondensing)
Without armor:
175mm x 97mm x 42mm
With armor:
180mm x 102mm x 52mm
Without armor: 267g
With armor: 362g
Meets IEC-529 IP-54 for dust and
water-resistant enclosures
EN61326-1/A1: 1998
(EU EMC Directive)
- 4 -

5. BATTERY INSTALLATION AND
REPLACEMENT
Voltages present at the thermistors may
also be present at the battery terminals.
Always disconnect the thermistor when
changing batteries.
Weak batteries should not be left in the
instrument. Dead batteries can leak and
cause damage to unit.
The typical battery life is about 700 hours.
Selected settings
will remain in memory
turned
off, or
replac
ed.
are
stored in
even after
while
batteries
memory and
power is
are being
1. Before
2.
3.
changing
off
and disconnect probe
Loosen screw and
the
back
of case.
Remove
the t
4. Insert three
pol
arity.
5.
Install
cover and
battery, tur
lift battery
hree
AA batteries.
new
batteries
tighten
- 5 -
n instrume
.
cover
observing
screw
.
nt
off

6. INSERTING AND REMOVING
OPTIONAL RUBBER ARMOR
1. To insert thermometer into the optional
rubber armor, slide in from the top of
meter before pushing the bottom edges
of meter down to set it into position. Lift
up the stand at the back of meter for
benchtop applications if necessary.
2. To remove thermometer from armor,
push out from the bottom edges of
meter until it is completely out of boot.
- 6 -