Wahl 2500MX User manual

W -683 Rev G
Revised 02/03/23
HEA T - PROBER
®
POR T ABLE THERMOCOUPLE
THERMOMETERS
INSTRUCTION MANUAL
LCD Models LED Models
2500MX
1370MX
2500M
2500MVX 1370MVX 1370M
3200MX 1770MX 3200M
3200MVX 1770MVX 1770M
TCMR-K
TCMR- KX
TCMRK-VX

RECEIVING INSPECTION
Check your new W ahl Portable Thermocouple 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 W ahl factor y of the difficulty . Give model number and description.
W ahl will authorize return, and notify our service department to receive the
unit.
2. Return the instrument in its shipping container to the factor y, freight pre-
paid. Repairs will be made under warranty or at regular service cost.
3. Prepare a “Repair Information Form” as shown in Section 12.0 and return
with the instrument. This is ver y important. W e need the information to
diagnose the problem. If there is no information returned with the unit, it
will slow up the repair process.
ii

T ABLE OF CONTENTS Page
RECEIVING INSPECTION . . . . . . . . . . . . . . . . . . . . . . .ii
1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
2.0 OPERA TION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
2.1 Meter Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
2.2 Peak Hold (MAXI-TEMP) . . . . . . . . . . . . . . . . . . . . . . . . . .5
2.3 Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
2.3.1 Recharging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
2.3.2 Low Batter y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
2.3.3 Continuous Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
3.0 PROBES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
3.1 Open Probe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
3.2 T emperature Sensors in use . . . . . . . . . . . . . . . . . . . . . . .11
4.0 SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . .14
5.0 CALIBRA TION . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
5.1 V oltage Regulator Adjustment . . . . . . . . . . . . . . . . . . . . . 17
5.2 Low Batter y Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . .17
5.3 Calibration Using W ahl Calibrator . . . . . . . . . . . . . . . . . . .18
5.3.1 Zero Adjustment Using W ahl Calibrator . . . . . . . . . . . . . . 18
5.3.2 Span Adjustment Using W ahl Calibrator . . . . . . . . . . . . . .18
5.4 Calibration With a Millivolt Sour ce . . . . . . . . . . . . . . . . . .18
5.4.1 Zero Adjustment with Millivolt Sour ce . . . . . . . . . . . . . . .18
5.4.2 Span Adjustment with Millivolt Sour ce . . . . . . . . . . . . . . .20
5.5 Thermal Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
5.6 Calibration with Thermocouple Simulator . . . . . . . . . . . . .22
5.7 T A-70 Thermocouple Calibrator . . . . . . . . . . . . . . . . . . . .22
6.0 THEORY OF OPERA TION . . . . . . . . . . . . . . . . . . . . . .27
6.1 V oltage Regulation Cir cuitr y . . . . . . . . . . . . . . . . . . . . . . .29
6.2 V oltage Reference Cir cuitr y . . . . . . . . . . . . . . . . . . . . . . .29
6.3 Front End Cir cuitr y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.4 Cold Junction Compensation . . . . . . . . . . . . . . . . . . . . . .30
6.5 Dual Slope A/D Converter . . . . . . . . . . . . . . . . . . . . . . . . .30
6.6 8048 Microprocessor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
6.7 Waveforms and T iming Diagrams . . . . . . . . . . . . . . . . . . .31
6.8 Low Batter y Indication . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
iii

7.0 BASIC TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . .33
8.0 MAINTENANCE AND REPAIR . . . . . . . . . . . . . . . . . . .36
8.1 LED and LCD Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . .36
9.0 APPENDIX IPTS-86 AND IPTS-90 . . . . . . . . . . . . . . . .42
10.0 ADDITIONAL PROBES AND ACCESSORIES . . . . . . . . .51
11.0
RETURN FOR REPAIR/CALIBRATION . . . . . . . . . . . . . .52
FIGURES Page
Figure 1-1 Microprocessor Based Thermocouple Digital Therm. . . . . .2
Figure 2-1 Digital Heat Prober Major Features . . . . . . . . . . . . . . . . . . .4
Figure 2-2 Rechargeable Batter y Pack Compartment . . . . . . . . . . . . . .6
Figure 3-1 Heat Prober Thermocouple T ypes, Model Numbers . . . . . .8
Figure 3-2 Standard W ahl Probes . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Figure 3-3 Extension Probe Handle . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Figure 3-4 Molten Metal Dip Stick . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Figure 5-1 W ahl Calibrator T ypes . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Figure 5-2 Heat Prober With W ahl Calibrator . . . . . . . . . . . . . . . . . . .24
Figure 5-3 LED Adjustment Points . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Figure 5-4 LCD Adjustment Points . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Figure 6-1 Program Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Figure 6-2 Microprocessor Control Functions . . . . . . . . . . . . . . . . . . .32
Figure 7-1 Wiring Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Figure 8-1 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
Figure 8-2 LED Component Layout . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Figure 8-3 LCD Component Layout . . . . . . . . . . . . . . . . . . . . . . . . . . .41
Figure 11-1 Additional Probes and Accessories . . . . . . . . . . . . . . . . . .50
iv

1
1.0 INTRODUCTION
W ahl Thermocouple Digital Heat-Prober Thermometers are precision Instruments for
measuring temperature, with special attention to ruggedness of design. They provide
the certainty of a digital display over the wide range of temperatures available with
thermocouples from -100°F to 3200°F (-70°C to 1770°C). The Heat-Prober is a com-
plete instrument with a battery power supply and recharger. It is inter changeable with
30 different thermocouple probe configurations designed for rapid sensing of temper-
ature in ever y application.
The Heat-Prober series accommodates two thermocouple types.
1. T ype K (Nickel Chromel-Nickel-Alumel) for general purpose use from
-100 to 2500°F (-70 to 1370°C).
2. T ype S (Platinum-Platinum/10% Rhodium), for high temperature use from
77 to 3200°F (25 to 1770°C).
All of the Heat-Prober instruments use common circuitr y. Microprocessors hold the
thermocouple tables in memor y and provide digital processing and control of the
information.
The instrument contains the unique W ahl MAXI-TEMP® digital peak cir cuit, which
gives the user the option to hold the highest temperature sensed. The peak-hold
cir cuit is achieved by the microprocessor scanning the probe input temperature to
determine the highest temperature reached. This peak is locked digitally and there is
no drift.
The meter has a convenient standard miniature temperature compensated connector
socket for easy use and inter changeability with similar thermocouple type probes.
A large portion of the cir cuit is designed with low power C-MOS components. In addi-
tion, the LED displays are multiplexed. The result is a design which provides a low
power drain and allows longer operation time on rechargeable batteries. Continuous
operation is also possible with the recharger attached. In both cases, the instrument is
powered from the batteries. Both LED and LCD models have a large character size for
good readability.

2
Figure 1.1. Microprocessor Based Thermocouple Digital Thermometer
(LED display, left; LCD display, right)

3
All Heat-Prober instruments are extensively tested in environments from
-20°F to 140°F for specification compliance and reliability determination. In addition,
durability testing includes impact, vibration, battery life and running life tests. Mean
time between failure is based on using preburned-in C-MOS electronic components
and is rated at 16,000 hours.
The 9-volt LCD models with 50-hour standard alkaline batteries, replaceable from the
back cover, are designated models 1370MVX, 1770MVX, 2500MVX and 3200MVX.
They have the same specifications as the rechargeable LCD models.
2.0 OPERA TION (See Figure 2-1)
Insert probe into socket at the top of the instrument. T u rn on the switch at the left. The
switch is 3-position; the lower detent is marked “N” for normal temperature monitor-
ing, the middle detent is “OFF’ and the upper detent is marked “P” for use with W ahl
Maxi-Temp peak hold cir cuit. This tracks the temperature and holds the highest attained
reading. If “L”, or “←”, appears or if there is no reading, this indicates the battery is
discharged. For models MVX, change the 9-volt battery. Recharge the unit by inserting
the recharger in a 110 V AC, 50-60 Hz wall outlet and plug in the recharger jack to the
instrument socket on the left. (T urn the instrument switch OFF during recharging, to
maximize recharge rate. Charge for 10-12 hours)*. T u rn on instrument again.
Make measurements with sensor probe as required. T u rn
off switch when measure-
ments are complete to preser ve battery life.
*Special Note on Care of Rechargeable Batteries, See Paragraph 2.3

4
Figure 2-1. Digital Heat-Prober Major Features

5
2.1 Meter Operation
The Heat-Prober instrument has an accurate measuring range as stated on the front
label. When the temperature is below zero, a minus sign will automatically show on
digital display. Absence of a sign indicates positive temperature.
2.2 Peak Hold (MAXI-TEMP)
MAXI-TEMP peak hold is a standard feature on all models. With the switch in “P” or
peak hold position, it will sense positive increases in temperature and hold the highest
reading. This is convenient in making measurements where attention to the probe or
to the area being measured occupies the operator. The peak reading is held digitally by
the microprocessor and will not drift. T o remove the peak reading, switch to “OFF”, or
to “N”.
2.3 Batteries (Figures 2-2)
The Heat-Prober is powered with five size AA rechargeable nickel-cadmium batteries,
1.25 volts each. The total capacity is 450 milliampere hours at 6.0 volts. The LED
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 6 hours (with LCD display, the life is approximately 12 hours).
An alternate replaceable 9-volt alkaline transistor radio-type battery powers meters
with “V” designations in their part number. The instrument has a voltage regulation
which will accept and control the power from the 9-volt battery. These instruments do
not allow for recharging. Under special cir cumstances LED models 2500M, 1370M
and 1770M may be operated with disposable 9-volt alkaline batteries with an approxi-
mate 3 hour battery Iifespan. (Figure 2.2)
SPECIAL NOTE: Rechargeable batteries should be kept at full charge. On the shelf,
they will gradually discharge, losing about 10% charge 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 W ahl P/N 11681 (See Figure 2-2).

6
Figure 2-2. Replaceable 9V Batter y Pack Compartment (above)
Rechargeable Batter y Pack Compartment (below)