Tenma 72-1025 User Manual

Benchtop LCR Meter

RS232

u
u

ALWAYS DISCHARGE THE CAPACITOR BEFORE TESTING

ON

OFF

FORCE

FREQ

FORCE

HOLD

REC

RS232

SENSESENSE

L/C/R

P SAUTO

RANGE TOL

CAL
REL

Model 72-1025

Tenma Test Equipment

405 S. Pioneer Blvd.

Springboro, OH 45066

www.tenma.com

i

Contents

Safety ................................................................................................... 1

Introduction........................................................................................... 3

Impedance theory................................................................................. 4

 Impedance ................................................................................ 4

 Measuring impedance ............................................................... 7

 Parasitic .................................................................................... 7

 Real, effective, and indicated values ......................................... 8

 Component dependency factors ..............................................10

 Measurement methods.............................................................16

Getting Started.....................................................................................17

 Front Panel Illustration .............................................................17

 Rear Panel Illustration ..............................................................18

 LCD Display Illustration ............................................................19

Measurement Preceedure ...................................................................21

 Inductance Measurement.........................................................22

 Capacitance Measurement......................................................23

 Resistance Measurement.........................................................24

Operating Instructions..........................................................................25

 Data Hold .................................................................................25

 Static Recording™....................................................................25

 Dissipation Factor / Quality Factor/ Phase Angle .....................26

 Test Frequency.........................................................................26

 L/C/R Function Selector ...........................................................26

 Relative Mode ..........................................................................26

 Tolerance Mode........................................................................27

 Auto / Manual Range................................................................28

 Automatic Fuse Detection ........................................................28

 Parallel / Series Mode ..............................................................29

 Short/ Open Calibration............................................................31

 Communication ........................................................................32

General Specifications.........................................................................33

Electrical Specifications.......................................................................34

 Resistance (Parallel mode) ......................................................34

 Capacitance (Parallel mode) ....................................................35

 Inductance (Series mode)......................................................37

ii

Accessories .........................................................................................39

Standard Accessories: ..................................................................39

Optional Accessories: ...................................................................40

MAINTENANCE ..................................................................................41

 Service .....................................................................................41

 Cleaning the Meter ...................................................................41

 Selecting input line voltage.......................................................42

 Fuse Replacement ...................................................................44

iii

SAFETY

Read "SAFETY INFORMATION" before using this meter.

 NOTE

The meter is a bench type instrument for testing inductance,

capacitance and resistance. If this device is damaged or something is

missing, contact the place of purchase immediately.

This manual contains information and warnings must be followed to

ensure safe operation as well as to maintain the meter in a safe

condition. Some common international electrical symbols used in this

manual are shown below Table:

DC - Direct Current

See Explanation In The Manual

Protective conductor

terminated.

Table-1. International Electrical Symbols

Before using the meter, read the following safety information carefully.

In this manual, "WARNING", is reserved for conditions and actions that
pose hazard(s) to the user; "CAUTION", is reserved for conditions and

actions that may damage your meter.

1

 SAFETY INFORMATION

To ensure that you use this device safely, follow the safety guidelines

listed below:

1. Before applying power, ensure that power cord and the proper line

voltage indicated for power source being used.

2. This product is grounded through the ground conductor of the power

cord. To avoid electric shock, the ground conductor must be

connected to earth ground. Before making any connections to the

input terminals, ensure that the unit is properly grounded.

3. To avoid personal injury, never operate the instrument without

covers or panels removed.

4. Do not operate this product in wet, damp or explosive atmosphere.

5. This meter is for indoor use, at altitudes up to 2,000m.

6. The warnings and precautions should be read and well understood

before the instrument is used.

7. Use this device only as specified in this manual; otherwise, the

protection provided by the meter may be impaired.

8. When measuring in-circuit components, first de-energize the circuits

before connecting test leads.

9. Discharge the capacitor before testing.

10. The meter is safety-certified in compliance with EN61010

(IEC-1010-1). EMC is certified in compliance with EN61326.

2

INTRODUCTION

This 19,999-count L/C/R meter is a special microprocessor-controlled

meter for measuring functions of inductance, capacitance and

resistance. Extremely simple to operate, the instrument not only takes

absolute parallel mode measurements, but is also capable of series

mode measurement. The meter provides direct and accurate

measurement of inductors, capacitors and resistors with selectable test

frequencies. It utilizes either auto and manual ranging.

Front panel pushbuttons maximize the convenience of function and

feature selection such as data hold; maximum, minimum and average

record mode; relative mode; tolerance sorting mode; frequency and

L/C/R selection.

The test data can be transferred to PC through an optional fully isolated

optical RS232C interface.

A tilt stand provides position flexibility for viewing and operating the

meter. Its portability and stackable design add ease of use by engineers,

communications technicians, schools and laboratories.

Figure- 1. Stackable Design

RS232

u

u

ALWAYS DISCHARGE THE CAPACITOR BEFORE TESTING

ON

OFF

FORCE

FREQ

FORCE

HOLD

REC

RS232

SENSESENSE

L/C/R

P SAUTO

RANGE TOL

CAL
REL

OFF

RS232

u

u

ON

ALWAYS DISCHARGE THE CAPACITOR BEFORE TESTING

FORCE SENSE SENSE FORCE

TOL

REC

HOLDRS232

AUTO P S

RANGE

FREQ L/C/R

CAL
REL

3

IMPEDANCE THEORY

 Impedance

Impedance is an important parameter used to characterize electronic

circuits, components, and the materials used to make components.

Impedance (Z) is generally defined as the total opposition a device or

circuit offers to the flow of an alternating current (AC) at a given

frequency, and is represented as a complex quantity, which is

graphically shown on a vector plane. An impedance vector consists of a

real part (resistance, R) and an imaginary part (reactance, X) as shown

in Figure-2.

Figure- 2. Impedance

Impedance can be expressed using the rectangular-coordinate form R+
jX or in the polar form as a magnitude and phase angle: |Z| ∠θ.

Figure-3 also shows the mathematical relationship between R, X, |Z|
and θ.

The unit of impedance is the ohm (Ω). Impedance is a commonly used

parameter and is especially useful for representing a series connection

of resistance and reactance, because it can be expressed simply as a

sum, R and X.

4

Figure- 3. Expression of series and parallel combination

Reactance takes two forms - inductive (XL) and capacitive (Xc). By

definition, X

L=2πfL and Xc=1/(2πfC), where f is the frequency of interest,

L is inductance, and C is capacitance. 2πf can be substituted for by the
angular frequency (ω:omega) to represent XL=ωL and Xc=1/(ωC). Refer

to Figure-4.

Figure- 4. Reactance in two forms - XL and Xc

Figure-5 shows a typical representation for a resistance and a

reactance connected in series. The quality factor (Q) serves as a

measure of a reactance’s purity (how close it is to being a pure

reactance, no resistance), and is defined as the ratio of the energy

stored in a component to the energy dissipated by the component. Q is

5

a dimensionless unit and is expressed as Q=X/R. From Figure-5, you
can see that Q is the tangent of the angle θ. Q is commonly applied to

inductors; for capacitors the term more often used to express purity is

dissipation factor (D). This D quantity is simply the reciprocal of Q. It is
the tangent of the complementary angle of θ.

Figure- 5. Relationships between resistance and reactance

6

 Measuring impedance

To find the impedance, we should measure two values at least because

impedance is a complex quantity. Many modern impedance instruments

measure the real and the imaginary parts of an impedance vector and
then convert them into the desired parameters such as |Z|, θ

, L, C, R, X, It is only necessary to connect the unknown component,

circuit, or material to the instrument. However, sometimes the

instrument will display an unexpected result (too high or too low). One

possible cause of this problem is incorrect measurement technique, or

the natural behavior of the unknown device. We will focus on the

traditional passive components and discuss their natural behavior in the

real world as compared to their idealistic behavior.

 Parasitic

There are no pure L, C or R. All circuit components are neither pure

resistive nor pure reactive, they are a combination of these impedance

elements. The result all devices have parasites - unwanted inductance

in resistors, unwanted resistance in capacitors, unwanted capacitance

in inductors, etc. Of course, different materials and manufacturing

technologies produce varying amounts of parasites, affecting both a

component’s usefulness and the accuracy with which you can

determine its resistance, capacitance, or inductance. A real-world

component contains many parasites. With the combination of a

component’s primary element and parasites, a component will be like a

complex circuit.

7

 Real, effective, and indicated values

A thorough understanding of real, effective, and indicated values of a

component, as well as their significance to component measurements,

is essential before you proceed with making practical measurements.

A real value is the value of a circuit component (resistor, inductor or

capacitor) that excludes the defects of its parasites. In many cases, the

real value can be defined by a mathematical relationship involving the

component’s physical composition. In fact, real values are only of

academic interest (Figure-6).

Figure- 6. Real capacitor value

The effective value takes into consideration the effects of a

component’s parasites. The effective value is the algebraic sum of the

circuit component’s real and reactive vectors; thus, it is frequency

dependent (Figure-7).

Figure- 7. Effective value

8

The indicated value is the value obtained with and displayed by the

measuring instrument; it reflects the instrument’s inherent losses and

inaccuracies. Indicated values always contain errors when compared to

true or effective values. They also vary intrinsically from one

measurement to another; their differences depend on a multitude of

considerations. Comparing how closely an indicated value agrees with

the effective value under a defined set of measurement conditions lets

you judge the measurement’s quality (Figure-8).

Figure- 8. Indicated value

The effective value is what we want to know, and the goal of

measurement is to have the indicated value to be as close as possible

to the effective value.

9

 Component dependency factors

The measured impedance value of a component depends on several

measurement conditions, such as frequency, test signal level, and so on.

Effects of these component dependency factors are different for

different types of materials used in the component, and by the

manufacturing process used. The following are typical dependency

factors that affect measurement results.

1. Frequency

Frequency dependency is common to all real components because of

the existence of parasites. Not all parasites affect the measurement, but

some prominent parasites determine the component’s frequency

characteristics. The prominent parasites will be different when the

impedance value of the primary element isn’t the same. The typical

frequency response for real resistors, capacitors and inductors is shown

as Figure-9, 10 and 11, respectively.

Figure- 9. Resistor frequency response

10

Figure- 10. Capacitor frequency response

Figure- 11. Indicator frequency response

11

2. Test signal level

The test signal (AC) applied may affect the measuring result for some

components. For example, ceramic capacitors are test signal voltage

dependent as shown in Figure -12. This dependency varies depending

on the dielectric constant (K) of the material used to make the ceramic

capacitor.

Figure- 12. AC voltage dependency for Ceramic capacitor

Cored-inductors are test signal current dependent due to the

electromagnetic hysteresis of the core material. Typical AC current

characteristics are shown in Figure-13.

Figure- 13. AC current dependency for Cored-inductor

12