Tenmars TM-508A User manual

MILLIOHM METER
TM-508A
HB2TM508A001
User’s Manual
TENMARS ELECTRONICS CO., LTD

CONTENTS
1Features ...................................................3
2General specifications..............................3
3Instrument description..............................5
4Notice in prior to the testing......................6
5Electrical specifications:...........................6
6Measurement by the Four Wire type one
pair of coated clip............................................7
7Precise Impedance measurement............8
8Battery Replacement................................9
9Replacement of fuse ..............................10
10 Maintenance and Care...........................10
11 END OF LIFE .........................................11

TM-508A
EN-3
1 Features
1. Very low impedance measurement by Four Wire
type one pair coated clip.
2. There is a fuse (0.5A/250V) to pro the input circuit.
3. Applicable measurement of Resistance, motor coil,
transformer, Printed Circuit Board.
4. Accurate measurement of conductor, light electricity
and welding point.
5. Wide measurement range, 0.1 mΩto 20kΩin 6
positions.
6. D –H Switch: Lockup readings for LCD display.
2 General specifications
1. Display:
3-1/2 digits, LCD display with
max. reading of 1999 with
decimal point and measurement
unit.
2. Overload
indication:
“OL” indication.
3. Zero Adjust:
External zero adjust knob.
4. Low battery
indication:
Replace battery as LCD display
“ ”
5. Reading speed:
2.5 times per second.
6. Operating
attitude:
Max. 2000 meters above level.
7. Operating
In-door use, under

TM-508A
EN-4
ambience:
environmental pollution grades
two.
8. Operating
temperature
and R.H. value:
5°C to 40°C, 80%RH or lower.
9. Storage
temperature
and R.H. value:
-10°C to 60°C, 70%RH or lower.
10.Power supply:
1.5V × 6 NEDA 15F IEC R6 JIS
SUM-3
11. AC adapter：
AC input Voltage is 100Vac to
240Vac 0.3A with input
frequency of 60 HZ or
50HZ,Free Voltage DC output is
9VDC(8~11VDCMax) Supply
current：＞0.5ADC. Socket：pin
Ground Casing Positive External
Diameter 3.5mm internal
Diameter 2.0mm
12. Dimension
and weight:
160 x 100 x 52mm. approximate
500g.
13. Accessories:
One set of testing clips and
instruction manual.
14. Fuse
specification:
0.5A/250V, 5Øx 20mm. FAST
MIN INTERRUPTS RATINGS
1500A.

TM-508A
EN-5
3 Instrument description
1. RX socket:
For testing clips input.
2. LCD display:
Indication of measured value and
unit.
3. ZERO ADJ.
Knob:
For zero adjustment.
4. Power switch
and Range
selector switch:
Selection in functional range of
the meter.
5. D-H:
Lock up the LCD reading.
6. DC Power
socket:
For AC adapter output DC Voltage
is 9VDC(8~11VDCMax).
FIG (1)

TM-508A
EN-6
4 Notice in prior to the testing
1. Don not connect the testing input terminals LO,
RX, RX, HI,) any input voltage directly, so as to
prevent any possible damage to the internal
circuits of the meter.
5 Electrical specifications:
( 23°C±5°C, 80% RH or lower )
Accuracy : ±( ……….% reading +……… digit):
Range
Accuracy
Resolution
Testing
current
Open Voltage
200mΩ
0.1mΩ
100mA
Approx.
4.8VDC
2Ω
1mΩ
10mA
20Ω
±(0.3%+
4dgt)
10mΩ
10mA
200Ω
0.1Ω
1mA
2kΩ
1Ω
1mA
20kΩ
10Ω
100uA

TM-508A
EN-7
6 Measurement by the Four Wire type one
pair of coated clip
To guarantee an higher precise measurement of
this digital Ohmmeter, an accurate wide range
impedance testing equipment, and to eliminate any
Improper Influence of measurement, especially in
effect of the impedance of testing leads, the
following procedures should be followed.
FIG(2)
1. Please refer to the table shown above, a
testing current is passed in individual testing
range (from HI end to the LO end).
2. The specific electric current flows through
any unknown resistance RX.
3. The Voltage VX can be measured on RX1,
RX2 terminals,
VX = RX x IS therefore RX = VX / IS
4. The unknown resistance value can be given
on LCD display from VX voltage value to be
measured.
5. To obtain accurate impedance measured
without any resistance value impedance

TM-508A
EN-8
between terminals RX1 and RX2.
7 Precise Impedance measurement
1. Insert an RED testing lead into “HI” socket and
another RED testing lead into the adjacent “RX”
socket; insert a BLACK testing lead into “LO”
socket and another BLACK testing lead into the
adjacent “RX” socket,
2. Select the function switch to 200 mΩposition.
3. Short circuit the two testing clips, adjust “ ZERO
ADJUST KNOB” (3-5) to a” 000” reading value on
the LCD.
FIG(3)

TM-508A
EN-9
4. Measure the resistance on PCB by using the
two-point type of measurement per shown in figure 4.
FIG(4)
5. The measured value is shown on LCD .
8 Battery Replacement
The meter is powered by 1.5V battery x6pcs (NEDA
15F IEC R6 JIS UM-3). Use the following procedure to
replace the battery:
1. Replace battery immediately when LCD displays
“ ”.
2. Turn the function switch to the "OFF" position.
3. Use a screwdriver to unfasten the screws on the
battery cover and remove the cover.
4. Take out the old batteries and replace with new
batteries, taking care to note the correct polarity.

TM-508A
EN-10
5. Re-install the battery cover and tighten the holding
screws.
9 Replacement of fuse
For a safety protection of the electrical circuit
please replace new fuse complying the
specification 0.5A/250V, 5Øx 20mm. FAST
MIN INTERRUPT RATINGS 1500A.
1. Select the function range switch to “OFF”
position. To unscrew the bottom case by
using a screwdriver.
2. Pull out the burned fuse and replace a new
one.
3. Close the bottom case and tighten screw.
10 Maintenance and Care
1.That all necessary requirements of inspection and
maintenance are not mentioned in this manual, a
qualified technician should perform it.
2.This meter is a precision digital instrument, whether
in use or in storage, please do not exceed the
specification requirements to avoid any possible
damage or danger during use.