Wahl HEAT-Prober 392EX-S, HEAT-Prober 392E, HEAT-Prober 392EVX, 392M, 392M-S Instruction Manual

HEAT-Prober

®

PLATINUM-RTD
T

HERMOMETERS

Models
392HP,

392E, 392E-S, 392EX, 392EX-S, 392EVX,

392M, 392M-S, 392MX, 392MX-S, 392VX,

360X and 700M

INSTRUCTION MANUAL

©Copyright 2004 Wahl Instruments, Inc. Printed in USA

W-392 (Rev. M)

ii

iii

RECEIVING INSPECTION

Check your new Wahl Portable Platinum HEAT-Prober®Thermometer upon
receiving to assure that:

1. It has not been physically damaged in transit.

2. All parts are included.

Then, plug in the probe at top and turn it on to see that it reads room tem­perature.
If a fault is determined, take the following steps:

1. Notify the Wahl factory of the difficulty. Give number and descrip­tion. Wahl will issue a Return Merchandise Authorization, and notify our serv­ice department to receive the unit.

2. Return the instrument in its shipping container to the factory,
freight prepaid. Repairs will be made under warranty or at regular service
cost.

W

ar

ranty: HEAT-Prober

®

Meters

Wahl Instruments, Inc., hereinafter referred to as Wahl, warrants each instru­ment of its manufacture to be free from defects in material and workmanship
under normal use and service. Wahl agrees to repair or replace any product
which upon examination is revealed to have been defective due to faulty
workmanship or material if returned to our factory, transportation charges
prepaid, within three years from the date of shipment. This warranty is in lieu
of all other warranties, expressed or implied and of all obligations or liabili­ties on its part for damages including but not limited to consequential dam­ages, following the use or misuse of instruments sold by Wahl. No agent is
authorized to assume for Wahl any liablility except as set forth above.

W

arranty: Temperature Probes and Meter Accessories

Wahl warrants its Hand-Held Meter Temperature Probes to be free of defects
in workmanship or material. Due to the environmental nature of their use,
probes cannot be replaced without cost unless returned unused within a 30­day period. Wahl assumes no liability for damages of any kind, direct or indi­rect, as a result of installation and/or use of its products; nor any costs
resulting from removing and reinstalling any of its products for replacement
under terms of this warranty.

TABLE OF CONTENTS Page

1.0 INTRODUCTION 1

1.1 Qualification Tests 1

1.2 Hazardous Location Operation 1

2.0 OPERATION 2

2.1 Meter Operation 2

2.2 Automatic Polarity 2

2.3 Digital Display and Accuracy 2

2.4 The Batteries 5

2.4.1 Recharging 5

2.4.2 Continuous Operation 5

3.0 PROBES 6

3.1 Interchangeability 6

3.2 Temperature Sensors in Use 7

4.0 SPECIFICATIONS

Model 392M, 392MX, 392VX,
392E, 392EX, 392EVX, 392HP Platinum Meters 8

5.0 MAINTENANCE/REPAIR 10

6.0 SETUP AND CALIBRATION 11

6.1 Equipment Needed 11

6.2 Voltage Regulator Adjustment 11

6.3 Low Battery Adjustment and Testing 11

6.4 Zero Adjustment Using Wahl Calibrator 12

6.5 Span Adjustment Using Wahl Calibrator 12

6.6 Adjustment Using Decade Resistance Box. 12

6.7 Peak Hold Circuit 13

6.8 Fahrenheit to Centigrade Conversion 16

6.9 Open Probe Display 16

6.9.1 “Help” Display 16

7.0 THERMAL CALIBRATION PROCEDURE 16

8.0 392HP and 392M OPTIONS 17

8.1 392HP 17

8.2 Degree F to C Conversions (Suffix D) 17

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 tempera­ture. It uses the latest microprocessor technology to provide conformity to

0.1°F to the IEC751 and ITS90 platinum resistance curve. It provides the cer­tainty 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 bat­tery 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 bat­tery 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 tempera­ture sensed. The peak-hold circuit is achieved by the microprocessor scan­ning the probe input temperature to determine the peak versus an analog cir­cuit.

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.

2

3

2.0 OPERATION (See Figure 2-1)

Insert probe into jack at top. Turn on the switch at the left. The switch is 3­position; the lower detent is marked “N” for normal temperature monitoring,
the middle detent is “OFF” and the upper detent is marked “P” for use of the
“Maxi Temp” Peak hold circuit. This will track temperature and hold the high­est attained reading. The room temperature will be displayed in °C or °F as
indicated. If “L” or “Lo Bat” appears or if there is no reading, this indicates
the battery is discharged. Recharge the unit by inserting the recharger in an
appropriate power source, 50-60 Hz wall outlet and plug in the recharger jack
to the receptacle on the left side of the unit, or in the case of the 392EVX or
392VX, replace the battery. For fastest recharging time, turn POWER for the
instrument OFF. Charge for 6-7 hours.

Make measurements with sensor probe as required. Turn off switch when
measurements are complete to conserve battery life.

2.1 Meter Operation

The HEAT-Prober instrument has an accurate measuring range as stated on
the front label. The probes, however, may not be capable of this entire range
of use. Wahl probes are typically capable of -40°C to 500°C (or -40°F to
900°F).

The digital readout will show resolution to 0.1° increments from

-180.0°C to +190°C (or -290°F to 375°F). At approximately 190°C (or 375°F)
the instrument automatically ranges to one degree C or F resolution. When
returning from higher temperatures to below 190°C (or 375°F), the instru­ment will automatically begin to read in 0.1° increments again.

2.2 Automatic Polarity

When the temperature sensed is below zero, a minus sign will automatically
show on the digital display. Absence of a sign indicates positive temperature.

2.3 Digital Display and Accuracy

The characteristic of digital readouts is a flicker in the least significant digit.
In this instrument, you can expect to see a 1-digit flicker, particularly when
reading 0.1 increments. Variations over 0.1 will be attributable to sensor tem­perature changes.

Figure 2-1. Digital Heat
Prober Major Features

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5

2.4 The Batteries

The 392HP, 392E, 392EX, 392M, and 392MX HEAT-Prober are powered with
five size AA rechargeable nickel-cadmium batteries, 1.2 volts each. The total
capacity is 650 milliampere hours at 6.0 volts. The display demands the
largest power drain. Depending on the number of digits being displayed, the
batteries can power the instrument for a minimum of 5 hours or for as long
as 8 hours.

The 392EVX and 392VX meter utilizes an LCD type display to conserve bat­tery life. Battery life is in excess of 50 hours of continuous use.

SPECIAL NOTE: Rechargeable batteries should be kept at full charge. On the
shelf, they will gradually discharge, losing about 10% per week. If the battery
fails to respond to recharge, provisions have been made for ease of replace­ment. Open the back cover, and disconnect from the instrument by means of
the Molex connector. Replace with Wahl Model Number 11681-1 or 11681-2
(See Figure 2-2). Model 392EVX and 392VX incorporates a LCD display and a
standard 9V battery capable of 50 hours continuous operation.

2.4.1 Recharging

To recharge the batteries, use the recharger supplied. Plug in directly to
115VAC, 60 cycle wall plug and insert jack into socket on left side of HEAT­Prober. (For overseas 220-volt lines, use a Franzus converter adapter with the
recharger supplied or request a 220 volt recharger.)

2.4.2 Continuous Operation

The 392HP, 392E, 392EX, 392M, and 392MX, HEAT-Prober can be continu­ously operated by using a battery recharger to restore or recharge the batter­ies as rapidly as they are depleted.

NOTE: The instrument cannot rectify AC current. A DC charger with open cir­cuit voltage of 9.0 volts and approximately 120 milliamperes will maintain the
battery charge. This occurs when the switch is on and the instrument is
operating. Do not connect a voltage source to the batteries unless its current
is limited to 120 milliamperes.

The MA-150 recharger will charge the batteries with the switch “OFF”, or
make-up battery drain if the instrument is operating. The recharger supplied
with the instrument will enable continuous operation without draining the
batteries.

Figure 2-2. 9V Battery Compartment (top picture); Rechargeable Battery
Pack Compartment (bottom picture).

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3.0 PROBES

Probes compatible with the 392 HEAT-Prober are constructed utilizing a wire
wound Platinum RTD sensor with an R0 of 100 Ohms wired in a 3-wire con­figuration to compensate for lead length effects. To provide probe inter­changeability at 0 degrees C, a balancing resistor is added to the sensor cir­cuit and trimmed for a total resistance of 100.94 Ohms at 0°C. (See Figure

3-2)

The High Performance HEAT-Prober, Model 392HP, utilizes probes similar to
the 392 but incorporating an additional calibration resistor that provides
probe interchangeability at all temperatures.

3.1 Interchangeability

Probes are individually balanced to 100.94 Ohms at 0°C to compensate for
variations in different probe configurations. This guarantees probe inter­changeability at 0°C. In addition, each probe is tested at a minimum of one
higher temperature. This calibration data is recorded on a calibration tag
attached to the probe. (See Figure 3-1)

Probe Interchangeability (Immersion)

Ice Point ±0.3°C (±0.5°F)—(392HP ±0.2°F)
100°C ±0.6°C (+1.0°F)
200°C ±1.1°C (±2.0°F)

Surface probes are tested on surface calibration plates especially built to
replicate the end-use. The variance is somewhat larger as follows:

100°C ±1.1°C (±2.0°F)
200°C ±2.2°C (±4.0°F)

Figure 3-2. Probe Circuit NOTE: Platinum sensor element manufacturers
quote 0.1% tolerance at 0°C, or 0.1 ohms on a 100 ohm sensor. This results
in 0.3°C variance. The tolerance at higher temperatures is greater than 0.1%
in accordance with the following formula as specified by DIN 43760:
Tolerance = ±.3°C + .0054t (°C)
Thus at 200°C, the expected sensor error could be 0.3°C + .0054 (200) =
±1.38°C.

3.2 Temperature Sensors in Use

An understanding of heat-transfer is needed for accurate field use of temper­ature sensors. The sensor measures its own temperature, therefore, to meas­ure a body temperature it requires good contact with that body, or in the case
of liquids or gases good immersion and mixing.

A portable probe temperature sensor must have the following characteristics:

(a) a low thermal mass (product of its specific heat and weight);
(b) a large area for surface contact to permit heat-transfer between the

object being measured and the probe sensor,

(c) a minimum of heat conduction away from the sensor which will
reduce its temperature below that of the object being measured and create an
inaccuracy.

Surface probes are designed with the above three conditions as criteria, and
also include an insulating handle for your safety and convenience. Each
probe is assembled with a plastic handle made of high quality Delrin

®

which:

(a) Thermally isolates the hand from the probe, preventing hand heat
from reaching the sensor, and sensor heat, in the case of high temperature
measurement, from burning the hand.

(b) Electrically isolating the hand from the metal probes and therefore,
potentially, from a voltage on the surface to be measured.

The handle is attached to a tangle-free retractable cord which extends 6' and
retracts to 12" (See Figure 2-1). Each Probe is labeled with its part number
and type.
For surface measurements, to obtain best time responses and accuracy, two
things are necessary;

(a) Good surface contact with all of the probe surface. Make sure of
this by holding it squarely on the surface. The 121 and 145 surface probes
are specially designed with a spring loaded tip to provide compliance with the
surface.

(b) A rough surface gives poor heat conductance to the measuring
probe. This can be overcome by applying a thin layer of heat conducting sili­cone paste between the measuring point and the probe tip. The paste short­ens response time up to 50%.

In liquids, move the immersion probe around the mix to get good contact. In
air, put the probe in the vicinity of a stream to get good velocity, other wise
move the probe back and forth to induce velocity across the tip.