Universal Enterprise DM391, DM393 Installation Manual

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DM391/393

INSTRUCTION MANUAL

Introduction

The DM391/ 393 are some of our safest industrial duty meters ever made.
All inputs, ranges and functions protected to 1000 Volts CAT III. Perfect for
H V AC and electrical technicians whose applications require higher
a c c u r a c y measurements and True RMS precision. Built in tempera t u r e
means one less instrument to bring to the job. The DM393 has convenient
access to battery and fuses without breaking ca l i b ration seals.

Features include

• All inputs, ranges and functions protected to 1000 V CAT III

• True RMS AC Volts and Amps

• Access to battery and fuses without breaking calibration

• Capacitance measurement from 40.00 nF to 100.0 µF

• 0.5% basic DC accuracy

• Frequency measurement to 10 MHz

• 4,000 count backlit display

• Autoranging

• Temperature from -40˚ to 2372˚F

• 4,000 count backlit display

Safety Notes

Before using this meter, read all safety information carefully. In
this manual the word "WARNING" is used to indicate conditions
or actions that may pose physical hazards to the user. The word
"CAUTION" is used to indicate conditions or actions that may
damage this instrument.

• Do not attempt to measure any voltage that exceeds the
ca t e g o ry b ased rating of this meter

• Do not attempt to use this meter if either the meter or the test
leads have been damaged. Turn it in for repair at a qualified
repair facility

• Ensure meter leads are fully seated by making a quick continuity
check of the leads prior to making voltage measurements

• Keep your fingers away from the test lead’s metal probe
contacts when making measurements. Always grip the leads behind
the finger guards molded into the probes

• Use a current clamp adapter when measuring current that may
exceed 10 amps. See the accessories in UEi’s full-line ca t a l o g

• Do not open the meter to replace batteries or fuses while the
probes are connected

WARNING!

Exceeding the specified limits of this meter is dangerous and can
expose the user to serious or possibly fatal injury.

• Voltages above 60 volts DC or 25 volts AC may constitute a
serious shock hazard

• Always turn off power to a circuit (or assembly) under test
before cutting, unsoldering, or breaking the current path ­Even small amounts of current can be dangerous

• Always disconnect the live test lead before disconnecting the
common test lead from a circuit

• In the event of electrical shock, ALWAYS bring the victim to
the emergency room for evaluation, regardless of the victim’s
apparent recovery - Electrical shock can cause an unstable heart
rhythm that may need medical attention

• Higher voltages and currents require greater awareness of

physical safety hazards - Before connecting the test leads; turn
off power to the circuit under test; set the meter to the desired
function and range; connect the test leads to the meter first, then
to the circuit under test. Reapply power

• If any of the following indications occur during testing, turn

off the power source to the circuit under test:

• Arcing

• Flame

• Smoke

• Extreme Heat

• Smell of Burning Materials

• Discoloration or Melting of Components

CAUTION!

Do not attempt to remove the meter leads from the circuit under test.
The leads, the meter, or the circuit under test may have degraded to
the point that they no longer provide protection from the voltage and
current applied. If any of these erroneous readings are observed,
disconnect power immediately and recheck all settings and connections

International Symbols

C o n t r ols and Indicators

NOTE: Although this manual describes the operation of the DM391 and
DM393, all illustrations and examples assume use of the DM393.

1. Digital Display: Readings are displayed on a digital, 4000
count display.

2. Push-button: Used for special functions and features.

3. Rotary Switch: A l l ows you to switch between any of the
functions or values indicated by the numbers, icons, and group
outlines printed around the rotating dial.

4. Input Terminal For 10A: ( 20A for 30 seconds) current
measurement function.

5. Input Terminal For Millii-amp and Micro Amps: Current
measurement function.

DM391/393-MAN P. 1

µA: Micro-amps AC rms and micro-amps DC

measurements (DM393)
Micro-amps AC and milli-amps DC
measurements (DM391)

mA: Milli-amps AC rms and milli-amps DC

measurements (DM393)
Milli-amps AC and milli-amps DC
measurements (DM391)

A: Amperes AC rms and amperes DC

measurements (DM393)
Amperes AC and amperes DC
measurements (DM391)

Push-Buttons

The buttons activate features that augment the function selected with
the rotary switch.

Range

Use the “RANGE” push-button to manually select a range. Press and
hold “RANGE” push-button for two seconds to return the meter to auto
range mode. The meter is in auto range mode when the “AUTO”
indicator is on. The “RANGE” selection function is not available in “Hz”
(Duty), “CAP”, and “Temp” modes.

The range and units are displayed on the LCD.

REL∆

Use this button to set the meter to relative (∆) mode and make relative
measurements. Relative zero allows the user to offset the meter
consecutive measurements with the displaying reading as the reference
value. Practically all displaying readings can be set as relative reference
value. Press the “REL∆” push-button momentarily to activate and to
exit relative zero mode.

Hz/Duty

Press this button to toggle between the “Hz” measurement mode and
the “Duty” measurement mode when the selector switch is set at “Hz”

(Duty), V, µA, mA, and 10A.

Hold

Press this button to turn “HOLD” mode ON and OFF. When the
“HOLD” mode is activated, the meter beeps, freezes the display and
displays the “D.H.” indicator on the LCD. Hold mode freezes the display
for later view.

(Backlight)

Press the “HOLD” ( ) push-button for two seconds to turn the
backlight ON or OFF, when the “HOLD” function is simultaneously
activated with the “D.H.” symbol on the display. Press the “HOLD”
push-button momentarily again to activate the backlight function only.

Select

Press this button to toggle between the DC measurement mode and the
AC measurement mode when the rotary selector switch is set to V
(DM393 only), µA, mA, and 10A. Press the “SELECT” push-button to

cycle through Ω, or measurement modes when the rotary
selector switch is set to Ω, , .

6. Common Input Terminal (ground reference): All
measurement functions.

7. Input Terminal for All Functions: Except current (A, mA, µA).

R o t a r y Switch

and Push-button Overv i e w

Turning the Meter On

To turn the meter on, turn the rotary switch from “OFF” to any
switch setting.

Rotary Switch

Turn the meter on by selecting any measurement function. The meter
presents a standard display for that function (range, measurement
units, etc.). Use the “SELECT” push-button to select any rotary switch
alternate function.

When you turn the rotary switch from one function to another, a display
for the new function appears. Button choices made in one function do
not carry over into another function.

Indicators

OFF: Turns the meter off

V: (DM393) AC volts RMS and DC volts. Press “SELECT”

push-button to choose AC or DC voltage

V: (DM391) AC volts

V: (DM391) DC volts

Ω : Access to resistance measurement, continuity test and

diode test

Hz (Duty): Frequency measurement. Duty cycle is also displayed if it

is toggled by the “Hz/Duty” push-button

CAP: Capacitance measurement

Temp: (DM393) Temperature measurement in degrees

Centigrade or Fahrenheit. Changing the reading mode
is preset at the factory

1

DM391/393-MAN P. 2

2

3

4

5

6

7

Operating Instructions

Voltage (V or V, V) Measurements

Voltage is the difference in electrical potential between two points. The
p o l a r i ty of AC (alternating current) voltage varies over time, while the

p o l a r i ty of DC (direct current) voltage is constant over time. V function
defaults at DC. Press the “SEL E CT” push-button momentarily to select AC .

Range available in volts function are:

400mV, 4V, 40V, 400V, and 1000V

When measuring voltage, the meter acts like a 10MΩ (10 x 10˚Ω)
impedance in parallel with the circuit. This loading effect can cause
measurement errors in high impedance circuits. In most cases, the
error is negligible (0.1% or less) if the circuit impedance is 10kΩ or less.

Tips for Measuring Voltage

• In 400mV range, displayed value may fluctuate while disconnecting
input terminals - This is normal

• AC voltage measuring circuit in DM393 is of root-mean-square
(True RMS) value systems so the meter can accurately measure
AC voltage of non-sinusoidal waveforms including harmonics
caused by various non-linear loads

• To improve the accuracy of DC voltage measurement taken in the
presence of AC voltages (such as, measuring the DC voltage of an
amplifier in the presence of an AC signal), measure the AC volt
age first. Note the just measured AC voltage range and select a
DC voltage rage that is the same or higher than the AC voltage
range - This method improves the DC voltage accuracy by
preventing the input protection circuits from being activated.

WARNING!

To avoid the risk of electrical shock and instrument damage, input
voltages must not exceed 1000 V DC or AC (RMS). Do not attempt to
take any unknown voltage measurement that may be in excess of
1000 V DC or AC (RMS).

Resistance (Ω, , ) Measurement
(Ohms, Diode, and Continuity)

DM391/393-MAN P. 3

WARNING!

To avoid damaging the meter or the equipment under test, remove all
power from the circuit and discharge all high-voltage capacitors before
measuring resistance.

Resistance is an opposition to current flow. The unit of resistance is the
ohm (Ω). The meter measures resistance by sending a small current
through the circuit.

Ranges available in resistance functions are:

4000.0Ω, 4.000 kΩ, 40.00 kΩ, 400.0 kΩ, 4 MΩ, and 40 MΩ

Tips for Measuring Resistance

• Because the meters test current flows through all possible paths
between the test prove tips, the measured value of a resistor in a
circuit is often different from the resistor’s rated value

• The test leads can add 0.1Ω to 0.2Ω of error to resistance
measurements - To measure the resistance of the leads, touch the
probe tips together and read the resistance - If necessary, you can
press the “REL∆” push-button to automatically subtract this value

• The resistance function can produce enough voltage to
forward-bias silicon diode or transistor junctions, causing them to
conduct - Do not use the 40 MΩ range for measuring the in-circuit
resistance to avoid this

• When measuring large resistance, reading may be unstable due to
environmentally induced electrical noise - In this case, directly
connect the resistor to input terminals of the meter or shield the
resistor at potential of the “COM” input terminal to obtain
stable reading

• For resistance above 1 MΩ, the display may take a few seconds
to stabilize - This is normal for high resistance readings

• The meter has a circuit to protect the resistance range from
over-voltage - However, to prevent accidentally exceeding the
protection circuit’s rating and to ensure a correct measurement,

NEVER CONNECT TH E LEADS TO A SOURCE OF VOLTAGE

when the rotary switch is set to Ω, , or functions