iv
1
TABLE OF CONTENTS (Continued)
8.3
Intrinsically Safe for Hazardous Location
(-S Versions)
17
8.4
Rate of Change with Hot and Cold
Peak Hold (Option R)
18
9.0
THEORY OF OPERATION
19
9.1
General
19
9.2
Program Flow
19
10.0
392M TROUBLE-SHOOTING AID
22
10.1
Scope
22
10.2
Procedure
22
11.0
ACCESSORIES
25
12.0
CALIBRATION SERVICE
26
13.0
THERMISTOR — .01°C RESOLUTION
HEAT PROBER (700M)
27
13.1
General Discussion
27
13.2
Calibration Procedure
29
13.2.1
Equipment Required
29
13.2.2
Calibration
29
14.0
700M TROUBLE-SHOOTING AID
29
15.0
WARRANTY REGISTRATION
32
16.0
RETURN FOR REPAIR/CALIBRATION
32
1.0 INTRODUCTION
The Digital HEAT-Prober
®
is a precision instrument for measuring tempera-
ture. It uses the latest microprocessor technology to provide conformity to
0.1°F to the IEC751 and ITS90 platinum resistance curve. It provides the cer-
tainty of digital display and the precision of 0.1 resolution. It is a complete
instrument with its own rechargeable battery power supply and recharger for
the 392HP, 392E, 392EX, 392M and 392MX, standard 9 volt replaceable bat-
tery for the 392EVX and 392VX and a group of interchangeable probes
designed for rapid and accurate temperature measurement.
The probes and meters are individually calibrated and then tested together in
temperature baths before being sent to the user.
The LED display is 0.33" high with high brightness for good readability in all
light conditions. To minimize power drain, the display is multiplexed. The
LCD display is 0.4" high with excellent contrast.
A large portion of the circuit is designed with low power C-MOS components.
The result is a design which provides a low power drain operation, which
allows operation for 8 hours per charge for the 392E, 392EX, 392M, and
392MX meters. Battery life is 50 hours for the replaceable battery used in the
392EVX and 392VX meters. Continuous operation as well as concurrent bat-
tery charging is possible by utilizing the recharger.
The instrument contains as a standard, the unique Wahl “Maxi Temp” digital
peak hold circuit which gives the user the option to hold the highest tempera-
ture sensed. The peak-hold circuit is achieved by the microprocessor scan-
ning the probe input temperature to determine the peak versus an analog cir-
cuit.
1.1 Qualification Tests
This instrument has been extensively tested under temperature environments
from -40 to +140°F, subject to 4-foot drop test, battery life test and running
life tests.
1.2 Hazardous Location Operation
The instrument is Factory Mutual approved for hazardous location operation
and carries the FM label as standard. Factory Mutual approval as intrinsically
safe for hazardous location operations is in the following categories: Class I
and II, Division I, Group D, F, and G when used with battery pack Part
Number 11681-1. A higher level of approval for Group C, D, E, F, and G is
also available as the -S version, and uses a battery pack, Part Number
11681-2, which contains, in addition, a current limiting fusible resistor.