Tegam AVM-2000 Troubleshooting guide

10 TEGAM WAY • GENEVA, OHIO 44041 440-466-6100 • FAX [phone] • www.tegam.com
AVM-2000
HIGH SENSITIVITY ANALOG DC VOLTMETER/NULLMETER
Instruction and Service Manual
PN# AVM2000-900
Publication Date: October 2010
REV. B

10 TEGAM WAY • GENEVA, OHIO 44041 440-466-6100 • FAX [phone] • www.tegam.com
TEGAM is a manufacturer of electronic test and measurement equipment for metrology, calibration, and
production test. We also provide repair, calibration, and other support services for a wide variety of test
and measurement equipment including RF power sensor calibration systems, RF attenuation measurement
systems, ratio transformers, arbitrary waveform generators, micro-ohmmeters, LCR meters, handheld
temperature calibrators, thermometers, humidity and temperature control devices, and more.
TEGAM also repairs and calibrates test and measurement equipment formerly manufactured by Electro-
Scientific Industries (ESI), Gertsch, Keithley Instruments, Lucas Weinschel, and Pragmatic Instruments. A
complete list can be viewed on our Product Service Directory at www.tegam.com
For more information about TEGAM and our products, please visit our website at www.tegam.com: or
contact one of our customer service representatives at [email protected] or 800-666-1010.
10 Tegam Way,
Geneva, Ohio 44041
Telephone: [phone]
Fax: [phone]
E-mail: [email protected]

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Table of Contents
Section Page
I. Introduction
Purpose and functions ........................................................................ 1-1
Capabilities....................................................................................... 1-1
Performance characteristics ................................................................ 1-2
Environmental information.................................................................. 1-3
Power and utility information............................................................... 1-4
List of items furnished........................................................................ 1-5
List of additional items required for operation and maintenance ............... 1-5
Preparation for calibration or repair and shipping ................................... 1-6
Expedite Repair Form......................................................................... 1-7
Warranty information ......................................................................... 1-8
TEGAM contact information ................................................................. 1-8
II. Preparation for Use and Installation
Unpacking & Inspection ...................................................................... 2-1
Recommended Operating Environment ................................................. 2-1
III. Principles of Operation
AVM-2000 measurement process......................................................... 3-1
IV. Operating Instructions
Front Panel Displays .......................................................................... 4-1
Front Panel Controls .......................................................................... 4-2
Normal Operation .............................................................................. 4-5
Setting Zero Procedure....................................................................... 4-6
V. Maintenance and Servicing
Maintenance ..................................................................................... 5-1
Disassembly and Re-Assembly ............................................................ 5-1
Calibration Verification ....................................................................... 5-4
Calibration........................................................................................ 5-7
Troubleshooting .............................................................................. 5-14
VI. Reprogramming
Total Instrument Reset (TIR) .............................................................. 6-1
Memory sanitization........................................................................... 6-1
VII. Preparation for Shipment
Returning power meter for service ....................................................... 7-1
Repacking for shipment...................................................................... 7-1

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VIII. Storage
Temperature and other environmental limitations .................................. 8-1
Safety Information & Precautions:
The following safety information applies to both operation and service personnel. Safety precautions and
warnings may be found throughout this instruction manual and the equipment. These warnings may be in
the form of a symbol or a written statement. Below is a summary of these precautions.
Terms in This Manual:
CAUTION statements identify conditions or practices that could result in damage to the equipment or
other property.
WARNING statements identify conditions or practices that could result in personal injury or loss of life.
Terms as Marked on Equipment:
CAUTION indicates a personal injury hazard not immediately accessible as one reads the marking, or a
hazard to property including the equipment itself.
DANGER indicates a personal injury hazard immediately accessible as one reads the marking.
Symbols:
As Marked in This Manual:
!
This symbol denotes where precautionary information may be found.
As Marked on Equipment:
!
CAUTION – Risk of Danger
DANGER – Risk of Electric Shock
Earth Ground Terminal
l
On
O
Off
Frame or Chassis Terminal
Earth Ground Terminal
Alternating Current

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1-1
Section I – Introduction
Purpose and Function
The AVM-2000 is a multi-range analog DC Voltmeter/Nullmeter. It has 21 bipolar ranges from ± 100
nanovolts full scale to ± 1000 volts full scale in a 1-3-10 sequence. The AVM-2000 functions either as an
isolated null detector or as an isolated analog voltmeter.
Key functions of the AVM-2000:
The AVM-2000 is a freestanding bench instrument housed in a protective metal enclosure. A single
unit may be mounted in a standard 19 inch rack using a conventional rack shelf.
Bail front feet allow the user to tilt the instrument for optimal viewing.
Voltage readings are displayed on a taut-band, zero-center, 4½ inch, mirror-backed, dual-scale
analog meter.
A rotary control provides selection of the instrument’s 21 ranges.
Instrument status (range, offset voltage, filter settings, battery condition, input impedance
selection, etc.) are displayed on a front panel LCD.
The AVM-2000 may be operated from the AC power line, an internal rechargeable battery or an
external DC source of 12 – 30 V. The instrument’s internal battery charger operates any time the
AVM-2000 is connected to a power source and the instrument is in a standby mode .
Voltages to be measured are applied to the AVM-2000 via low-thermal EMF front panel input
terminals—HI and LO. A GUARD terminal is provided to connect input wiring shields.
A FILTER selection feature allows the operator to choose signal filtering from 0.1 to 100 seconds to
improve measurements.
An OFFSET feature allows the user to offset a wide range of input voltages.
An OPERATE/ZERO switch allows the user to disconnect the HI input terminal from the amplifier
input and short the amplifier input to input common (LO). The user may select any one of 4
different input impedances for ranges below 3 mV and either 10 or 100 MΩfor ranges of 3 mV to
300 V. The 1 kV range input impedance is fixed at 100 MΩ.
A multi-mode INPUT OFFSET control allows the user to adjust the instrument’s zero (voltage) for
the current range, to inject an input offset current of up to ± 2.5 nA to offset the effects of input
bias currents on high impedance voltage sources or to select the digit of offset voltage to be
changed.
A two-terminal rear panel output is provided for use with external devices such as chart recorders,
remote data acquisition systems, digital readouts, etc. This output allows the AVM-2000 to function
as a high sensitivity instrumentation amplifier with gains that are the inverse of the input
attenuator settings. These two terminals are an ISOLATED OUTPUT. A third rear panel terminal is
connected to the case. A front panel control allows adjustment of the full scale output level from ±
0.5 volts to ± 1.5 volts.
Capabilities
The AVM-2000 is designed for the calibration laboratory. By utilizing a unipolar, high gain, low drift
amplifier coupled with the ability to attenuate or amplify the input voltage makes the AVM-2000 ideal for
nulling applications/calibrations. This is ideal for comparing an unknown to a known (comparing a 10 V
source to a voltage standard).

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1-2
Section I – Introduction
Specifications
(Includes performance characteristics, description, power and utility information and
environmental information)
Table 1.1 Physical and Electrical Specifications
Inputs and Ranges • One set of input terminations for all ranges
• HI LO & Guard
• Low end 100nV full scale deflection with 2nV resolution
• High-end range ≥1000V full scale deflection. with 5V or better resolution
• 21 selectable ranges, (1-3-10 sequence)
Outputs and Indicators 2 output indications
• Analog meter
• Isolated analog rear panel output
Analog Output Accuracy
Resolution
Linearity
± 0.5% of full scale of range selected (typically 0.1%)
Within 0.1% of full scale of selected range (after floor noise compensation)
Within 0.5% of full scale of selected range
Analog Meter Accuracy1
Scaling
Linearity
Resolution
± 2% of full scale of selected range
Mirrored zero center 10-0-10 and 3-0-3
≤± 1% of full scale of selected range
≤1% of full scale of selected range (typically, 0.5% of full scale of selected
range)
Meter Response Time2(To 90% of final reading)
100 nV - 1 μV full scale: 5 seconds
3 μV full scale: 3 seconds
All other ranges: 1.5 seconds
Input Impedance
100 nV to 1 mV FS
3 mV to 300 V FS
1 KV FS
1 MΩ, 10 MΩ, 100 MΩ, or 1 GΩSelectable +/- 10%
10 MΩor 100 MΩ+/- 5%
100 MΩ+/- 5%
Offset Current Adjustable (± 2.5 nA) to zero at front panel
Filter
10-position digital low pass filter selectable from front panel 100, 200, 500
mSec, 1, 2, 5, 10, 20, 50, 100 Sec
Offset
Resolution
Accuracy
Continuously variable (0 to ±999.9% of range) offset for all ranges
≤.01% of offset full scale
≤±0.5% of offset full scale
Series Mode Rejection > 80dB at 50Hz-60 Hz
1Meter specification measurements and terms per ANSI C39.1
2With filter response time set to 100 ms. Otherwise, filter response times add to meter response time.

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1-3
Section I – Introduction
Instrument Noise 400 pV (peak-to-peak, shorted input33) RTI
Equivalent noise source approximately 30 ohms
Outputs Isolated yielding ±0.5 to ±1.5V (user adjustable) for full scale deflection
Isolation Input to case or output > 100 GΩ(typically > 500 GΩ)
Overload Protection 1100 VDC or peak on any range
Indicators
Meter: 4 ½” Mirror Backed with – 3 –- 0 –- +3 and -10 –- 0 –- +10 Scales
Status Backlit LCD: Range, Offset, Filter Response Time, Input Impedance,
ZERO/OPERATE Mode, Input Offset Mode and Isolated
Output Mode
Dimensions 6.5” H X 11.5”W X 13.5” D
Weight 22.5 lbs
Connectors • Low thermal EMF input terminals plus guard
• Two output Binding Posts, plus a third for case common
• Input terminal cover
Power Supply • Internal rechargeable battery
• External 12 to 30 V DC @1.25 Ampere
• External “Power Cube” included
Environmental Operating Temperature Range: 15 - 30 °C Full Specifications
Operating Humidity Range: 0 - 50% RH Full Specifications
Storage Temp / Humidity: -20 to + 60 °C / 0 - 80% non- condensing
3Inputs shorted by a low EMF strap firmly connected between HI and LO input connections. (Lesser performance may be experienced when shorted input is
accomplished by ZERO switch). Constant temperature.

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1-4
Section I – Introduction
Line Voltage Selection:
The AVM-2000 is delivered with an AC Power Module for operation from 120 ±10% VAC, 60 Hz. If
the AVM-2000 is to be operated from a 240 ±10% VAC, 50-400 Hz power source, or the input
power range needs to be changed from a previous selection, an alternative AC Power Module is
required. Contact TEGAM for a selection of input Power Modules.
CAUTION: DO NOT APPLY POWER TO THE INSTRUMENT BEFORE READING THIS SECTION.
Check the Power Cord
Make sure the power cord supplied with the Model AVM-2000 is not frayed, broken, or cracked. A
damaged power cord is a fire and electrical hazard. If the power cord is damaged, it should be
replaced.
Use the Proper Fuse
To avoid fire hazard, use only the correct fuse type as specified for the AC power supply in the unit.
The correct fuse for the AVM-2000 is a 1 1/4A, 3AG Slow Blow Fuse.
The fuse is located just below the power cord socket. Before replacing the fuse, place the Model
AVM-2000 front panel power switch to the OFF position and remove power cord on the back of the
Model AVM-2000. To replace the fuse, gently slide out the fuse drawer. Remove the old fuse and
snap a new one into the fuse holder. Reinstall the fuse by simply pushing the fuse drawer back into
its original position. The fuse drawer should snap into place.
Grounding the Equipment
ISOLATED OUTPUT
Two (Red and Black) binding posts with banana sockets (4mm) are provided to connect the AVM-
2000’s ISOLATED OUTPUT to an external device. A third (Yellow) binding post connected to the
AVM-2000 case which may be connected to earth ground via other connections to the instrument.
The ISOLATED OUTPUT red and black binding posts are electrically isolated from the HI and LO
input terminals. The signal level present at the ISOLATED OUTPUT is adjustable, via the OUTPUT
LEVEL control, from ± 0.5 V to ±1.5 V full scale for the RANGE selected. The ISOLATED OUTPUT
zero reference is adjusted during the Setup mode using the OUTPUT LEVEL control.
WARNING: To avoid electrical shock or other potential safety hazards, plug the power cord into a
properly wired receptacle before using this instrument. The proper grounding of this instrument is
essential for safety and optimizing instrument operation.
WARNING: Applying more than 1100 Volts across the input terminals or from either input terminal
to common or ground results in instrument damage not covered by the warranty.
NOTE: Rapid changes in input voltage potentially can result in voltages well in excess of 1100 Volts
due to reactive effects in the supply circuit—such induced voltage may damage the instrument.
!

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1-5
Section I – Introduction
Items Included with the AVM-2000
Item Part Number
AC Power Module
Rechargeable Battery
Input Terminal Shield
GUARD to LO Nickel Plated Shorting Link
2 μF Filter Block Mounted on Dual Banana Jack
Technical (Instruction and Service) Manual
PS-107
BA-105
0600-081
J-5
0600-090
AVM2000-900
Table 1.2— AVM-2000 Packing List
Additional items required for operation and maintenance
Precision voltage and current source 0 to 1000 Volts DC & AC RMS and 10 μA – 1 A DC, such as
Fluke model 5100 or 5720 Multi Product Calibrator
Precision DMM with range of 0 to ±1000 V DC and AC RMS such as Fluke model 8508A, Keithley
2002 or Agilent 3458A.
Oscilloscope such as Tektronix model TDS-1000
Environmental chamber capable of housing the AVM-2000 with ability to regulate temperature from
10°C to 35°C ±0.1°C such as Thermotron model S-5.5 3800
Megohmmeter such as PPM model R1M-A
Low-thermal EMF shielded test leads (solid copper wire or solid copper wire with gold plated spade
terminals)
Pure copper shorting strap
10 mΩ10 A shunt, 0.1%
25 Ωresistor, ¼ Watt, 1%
30 Ωresistor, ¼ Watt, 1%
10 kΩresistor. ¼ Watt, 1%
1 MΩresistor, ¼ Watt, 1%
10 MΩresistor, ¼ Watt, 2%
100 MΩresistor, ¼ Watt, 2%

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1-6
Section I – Introduction
Preparation For Calibration Or Repair Service
Once you have verified that the cause for the AVM-2000 malfunction cannot be solved in the field and the
need for repair and calibration service arises, contact TEGAM customer service to obtain an RMA,
(Returned Material Authorization), number. You can contact TEGAM customer service via the TEGAM
website, www.tegam.com or by calling 440.466.6100 (All Locations) OR 800.666.1010 (United States
Only).
The RMA number is unique to your instrument and will help us identify you instrument and to address the
particular service request by you which is assigned to that RMA number.
Of even importance, a detailed written description of the problem should be attached to the instrument.
Many times repair turnaround is unnecessarily delayed due to a lack of repair instructions or of a detailed
description of the problem.
This description should include information such as measurement range, and other instrument settings,
type of components being tested, are the symptoms intermittent, conditions that may cause the
symptoms, has anything changed since the last time the instrument was used, etc. Any detailed
information provided to our technicians will assist them in identifying and correcting the problem in the
quickest possible manner. Use a copy of the Repair and Calibration Service form provided on the next
page.
Once this information is prepared and sent with the instrument to our service department, we will do our
part in making sure that you receive the best possible customer service and turnaround time possible.

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1-7
Section I – Introduction
EXPEDITE REPAIR & CALIBRATION FORM
Use this form to provide additional repair information and service instructions. The Completion of this
form and including it with your instrument will expedite the processing and repair process.
RMA#: Instrument Model #:
Serial
Number:
Company:
Technical Contact: Phone Number:
Additional
Contact Info:
Repair Instructions:
Evaluation Calibration Only Repair Only Repair & Calibration Z540 (Extra Charge)
Detailed Symptoms:
Include information such as measurement range, instrument settings, type of components being
tested, is the problem intermittent? When is the problem most frequent?, Has anything changed with
the application since the last time the instrument was used?, etc.

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1-8
Section I – Introduction
Warranty
TEGAM, Inc. warrants this product to be free from defects in material and workmanship for a period of one
year from the date of shipment. During this warranty period, if a product proves to be defective, TEGAM
Inc., at its option, will either repair the defective product without charge for parts and labor, or exchange
any product that proves to be defective.
TEGAM, Inc. warrants the calibration of this product for a period of 1 year from date of shipment. During
this period, TEGAM, Inc. will recalibrate any product, which does not conform to the published accuracy
specifications.
In order to exercise this warranty, TEGAM, Inc., must be notified of the defective product before the
expiration of the warranty period. The customer shall be responsible for packaging and shipping the
product to the designated TEGAM service center with shipping charges prepaid. TEGAM Inc. shall pay for
the return of the product to the customer if the shipment is to a location within the country in which the
TEGAM service center is located. The customer shall be responsible for paying all shipping, duties, taxes,
and additional costs if the product is transported to any other locations. Repaired products are warranted
for the remaining balance of the original warranty, or 90 days, whichever period is longer.
Warranty Limitations
The TEGAM, Inc. warranty does not apply to defects resulting from unauthorized modification or misuse of
the product or any part. This warranty does not apply to fuses, batteries, or damage to the instrument
caused by battery leakage.
Statement of Calibration
This instrument has been inspected and tested in accordance with specifications published by TEGAM Inc.
The accuracy and calibration of this instrument are traceable to the National Institute of Standards and
Technology through equipment, which is calibrated at planned intervals by comparison to certified
standards maintained in the laboratories of TEGAM Inc.
Document publishing dates may lag product changes.
Visit www.tegam.com to download the latest version of this manual.
Contact Information:
TEGAM INC.
10 TEGAM WAY
GENEVA, OHIO 44041
PH: 440.466.6100
FX: 440.466.6110
EMAIL: [e-mail]
WEB: http://www.tegam.com

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2-1
Section II – Preparation for Use and Installation
Unpacking & Inspection
Each AVM-2000 is put through a series of electrical and mechanical inspections before shipment to the
customer. Upon receipt of your instrument unpack all of the items from the shipping carton and inspect for
any damage that may have occurred during transit. Report any damaged items to the shipping agent.
Retain and use the original packing material for reshipment if necessary.
Upon Receipt, inspect the carton for the following items:
Model AVM-2000 RF Power Meter
AC Power Module
Rechargeable Battery
Input Terminal Shield
GUARD to LO Nickel Plated Shorting Link
2 μF Filter Block Mounted on Dual Banana Jack
Technical (Operation and Maintenance) Manual
Mounting
The AVM-2000 is a free-standing bench instrument housed in a protective metal enclosure. A single unit
may be mounted in a standard 19 inch rack using a conventional rack shelf. Bail front feet allow the user
to tilt the instrument for optimal viewing.
Use in Proper Environment
Normal calibration laboratory practice dictates that the environment should be closely controlled. This will
minimize errors introduced by temperature and humidity changes. A nominal temperature of 15 - 30 °C
provides a good working condition.
CAUTION: The AVM-2000 has a specified ambient temperature range 15 - 30 °C. Operating beyond these
limits can affect the accuracy of the instruments and damage internal circuitry.
CAUTION: When the AVM-2000 is to be stored for extended periods, pack the instrument into a container.
Place container in a clean, dry, temperature-controlled location. If instrument is to be stored in excess of
90 days, place desiccant with items before sealing container. The safe environmental limits for storage are
-20° to +60°C and 0% to 80% non-condensing relative humidity.
Do Not Use in Explosive Environments
CAUTION: The AVM-2000 is not designed for operation in explosive environments.
Ensure Power Switch is Accessible
CAUTION: Ensure that the POWER switch is easily accessible at all times and nothing is in place that would
impede proper use.
Do Not Operate Without Covers
WARNING: This device should be operated with all panels and covers in place. Operation with missing
panels or covers could result in personal injury.

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3-1
Section III – Principles of Operation
Understanding the AVM-2000 Measurement Process
Basic operation of the AVM-2000 and an understanding of how it achieves its specified levels of
performance follow. The AVM-2000 architecture consists of three main sections: an Isolated Analog
Subsystem; a Front Panel Subsystem; and a Power Supply Subsystem. The Isolated Analog Subsystem is
optically (and therefore electrically) isolated from the balance of the instrument to ensure minimum noise
introduction into the measurement signals from control/digital signals and to ensure that, when operating
as a floating null meter, the impedance to chassis/earth ground from either of the two input terminals is
extremely high.
The heart of the AVM-2000 is in the Isolated Analog Subsystem. This is where nano-volt level signals are
amplified via low-drift, low-noise, amplifiers to a level where they can drive a wide dynamic range 24-bit
analog-to-digital converter and where initial analog filtering (10 Hz 4-pole Butterworth, low-pass) is
applied. Once the signal is in digital format, it is further filtered, scaled and transferred across the isolating
boundary for meter display and rear panel output as a high-speed serial signal. An ISOLATED OUTPUT is
available so the AVM-2000 may be operated as a high-gain instrumentation amplifier with isolated output.
When used as an instrumentation amplifier, the amplifier’s gain is the inverse of the AVM-2000’s range
control setting. For example, at the 1 μV range and with the ISOLATED OUTPUT set to 1 V for full scale
response, the amplifier gain is 1 V / 1 μV = 1,000,000.
Input signals are applied to the AVM-2000’s low-thermal EMF binding posts. From here the signals are
routed directly to the programmable input attenuator. Depending on the selected measurement range, the
input signal is applied directly to the input amplifier (100 nV – 1 mV ranges) via a matched set of low-
thermal EMF polarity reversal relays, or is attenuated to be compliant with the input amplifier’s dynamic
range and then applied to the input amplifier (3mV – 1000V). On all ranges, all stages of the input
amplifier allow sufficient head room so peak noise does not cause limiting and very high loop gains ensure
low-distortion. This allows the AVM-2000 to make full use of the digital filtering technology to eliminate
unwanted noise from the measured signals.
Before signals are applied to the input amplifier, they pass through input protection circuitry. This protects
the input amplifier from the direct application of excess voltage (up to 1,100 VDC/peak) on any input
range. Additionally, the AVM-2000 input attenuator can be configured (in the 100-nV to 1-mV full scale
ranges) as a 1 MΩ, 10 MΩ, 100 MΩor 1 GΩinput termination resistance (user selectable). Input
impedances for ranges between 3 mV full scale and 300 V full scale are 10 MΩor 100 MΩ. The 1 kV range
input impedance is fixed at 100 MΩ.
Signals that are to be applied directly to the amplifier pass through a matched set of polarity reversing
relays. When measuring signals on ranges of 1 mV or less, one half of all measurements are made with
the relays in the NORMAL configuration and one half of all measurements are made with the relays in the
ALTERNATE (polarity reversal) configuration. When the respective signals are digitized, they are
subtracted from each other thus minimizing the impact of noise, thermal drifts and other undesired signals
that tend to be of a single polarity. Further, averaging of these responses also minimizes the impact of
drift.
Amplification of the input signal occurs in a low-noise, low-drift, multi-stage programmable gain amplifier.
The input amplifier housing is shielded to ensure minimal impact from external electro-magnetic signals
and short-term temperature changes in the operating environment. The amplifier components are chosen
to ensure Johnson Noise and other similar noise contributors fall below an equivalent noise resistance of
25Ω.
Early stages of the input amplifier are provided with basic filtering that permits the amplifier to maintain
its DC performance characteristics with the simultaneous application of a line-frequency (50 Hz or

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3-2
Section III – Principles of Operation
greater)signal up to 80 dB greater than the signal being measured. Precise and highly-stable offset
current is also applied to the input amplifier via a 16-bit DAC whose output value is set by the front panel
INPUT OFFSET control.
The output of the multi-stage amplifier is applied to the input of a precision 24-bit analog-to-digital
converter. This high-precision, high-stability analog-to-digital converter samples the input signal (including
input noise) many times per second. Various filtering/averaging algorithms are applied to this 24-bit result
based on front panel FILTER settings. The processor then converts the 24-bit word into a bit stream that is
optically coupled to the Front Panel Subsystem. The 24-bit conversion gives a resolution in excess of one
part in 16 million to provide a high degree of overall linearity and resolution (ultimately, after processing,
18 bits—17-bits of amplitude resolution and one sign bit). The 24-bit conversion allows extensive digital
filtering and manipulation to assist in the measurement and noise reduction process.
Once the digitized (and optically isolated) measurement information is received by the Front Panel
Subsystem the output is converted from serial information and is sent to a 20-bit digital-to-analog
converters with updates every 200 mS. The digital-to-analog converter output is buffered and sent to the
4 ½ inch, zero-center, mirror-backed meter movement. This meter provides a high-resolution readout
with both 10 – 0 – 10 and 3 – 0 – 3 scales. A second 20-bit digital-to-analog converter output is sent to a
buffer amplifier. This output is normalized to ±1 V at full scale (corrected for any gain normalizations set
by the operator who can make gain adjustments which set the ISOLATED OUTPUT full scale level at ±0.5
V - ± 1.5 V for a full scale input) and is applied to the ISOLATED OUTPUT rear panel terminals. This output
allows the operator to utilize the AVM-2000 as a high-gain, high-linearity, (chopper-stabilized for ranges of
1mV and below) instrumentation amplifier with isolated output. A front panel knob allows operator
adjustment of the isolated output amplitude.
The Front Panel Subsystem control circuits consist of a microprocessor, LCD, 6 pushbuttons and 3 rotary
encoders. The microprocessor continuously scans the switches and rotary encoders to detect any changes.
It also regularly updates the LCD with the current AVM-2000 status as selected by the user with the
pushbuttons and rotary encoder.
The microprocessor regularly poles the Isolated Analog Subsystem via a high-speed optically isolated
serial communications bus. The Isolated Analog Subsystem responds, supplying the results of the current
analog to digital conversions of the applied input signal. In addition to polling the Isolated Analog
Subsystem, Front Panel Subsystem communications include information such as current RANGE, FILTER,
OFFSET, OPERATE/ZERO, ZIN, and ZERO selections. When operated in the setup mode (special menu on
the LCD selected by depressing the Range Control), the microprocessor communications are modified to
contain special requests such as ZERO, GAIN and setting the 2.667 volt reference.

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4-1
Section IV – Operating Instructions
Front Panel Displays
LCD Display:
Instrument operating status is indicated on the front panel LCD. Information displayed includes:
RANGE : 21 Ranges from 100 nV to 1 kV (full scale)
INPUT IMPEDANCE: 1, 10, 100 MΩ, 1 GΩor ZERO (Shorted input)
OFFSET: ±30,000.00 μV in 0.01 μV steps
BATTERY STATUS: Vertical bar graph showing 0 – Full Charge
VARIABLE CONTROL LOCK: Status of variable control locks
FILTER: Filter times from 0.1 s to 100 s in 1-2-5 sequence
Power ON indication is also on the LCD display indicating the amount of battery life remaining. The LCD
blinks CHARGING if the instrument is connected to a charging source with power turned OFF. The battery
graph indicates ERR if the battery voltage is abnormally low with charging current applied.
Analog Display:
Voltage readings are displayed on a taut-band 4 1/2 inch, zero center, mirror-backed meter with dual
scales (± 0 - 3 or ± 0 – 10). The scale used depends on the range selected.
Figure 4.1 - AVM-2000 Front Panel

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Section IV – Operating Instructions
Front Panel Controls
Power -- Pushbutton
Push ON / Push OFF
RANGE/PUSH FOR MENU -- Rotary Control/Pushbutton
This is a multi-function button and should be thoroughly understood prior to operating any other controls
on the AVM-2000.
Range:
In the default position, meaning the rotary button was not pressed only rotated, the rotary control button
selects one of 21 full scale voltage ranges: 100 nV, 300 nV, 1 μV, 3 μV, 10 μV, 30 μV, 100 μV, 300 μV, 1
mV, 10 mV, 30 mV, 100 mV, 300 mV, 1 V, 3 V, 10 V, 30 V, 100 V, 300 V, 1 kV (1000 V). The selected
range full-scale value displays on the LCD.
Push For Menu:
This control performs secondary functions such as instrument setup routines. To access to these functions
depress the RANGE control for approximately 5 seconds, after which the set up menu appears in the LCD.
Rotating the RANGE control in this mode causes the LCD to display various setup options.
FILTER -- Pushbuttons
Two momentary action FILTER pushbuttons allow the user to increase (+) or decrease (-) the filter
setting. Filter integration time is shown on the LCD. The available filters: 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50,
and 100 seconds. An input signal is averaged (running average) before driving the meter movement or
isolated output over these times.
NOTE: Input ranges of 10 μV and below have a restricted range of filter times (see Table 4-1).
Range Filter Input Ω
100nV 2 sec to 100 sec 1MΩ, 10MΩ, 100MΩ, 1GΩ
300nV 2 sec to 100 sec 1MΩ, 10MΩ, 100MΩ, 1GΩ
1μV 1 sec to 100 sec 1MΩ, 10MΩ, 100MΩ, 1GΩ
3μV 0.5 sec to 100 sec 1MΩ, 10MΩ, 100MΩ, 1GΩ
10μV 0.5 sec to 100 sec 1MΩ, 10MΩ, 100MΩ, 1GΩ
30μV 0.1 sec to 100 sec 1MΩ, 10MΩ, 100MΩ, 1GΩ
100μV 0.1 sec to 100 sec 1MΩ, 10MΩ, 100MΩ, 1GΩ
300μV 0.1 sec to 100 sec 1MΩ, 10MΩ, 100MΩ, 1GΩ
1mV 0.1 sec to 100 sec 1MΩ, 10MΩ, 100MΩ, 1GΩ
3mV 0.1 sec to 100 sec 10MΩ, 100MΩ
10mV 0.1 sec to 100 sec 10MΩ, 100MΩ
30mV 0.1 sec to 100 sec 10MΩ, 100MΩ
100mV 0.1 sec to 100 sec 10MΩ, 100MΩ
300mV 0.1 sec to 100 sec 10MΩ, 100MΩ
1V 0.1 sec to 100 sec 10MΩ, 100MΩ
3V 0.1 sec to 100 sec 10MΩ, 100MΩ
10V 0.1 sec to 100 sec 10MΩ, 100MΩ
30V 0.1 sec to 100 sec 10MΩ, 100MΩ
100V 0.1 sec to 100 sec 10MΩ, 100MΩ
300V 0.1 sec to 100 sec 10MΩ, 100MΩ
1000V 0.1 sec to 100 sec 100MΩ
Table 4-1 - Table of Ranges, Input Impedance and Available Filter Settings

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Section IV – Operating Instructions
OFFSET -- Pushbuttons
Two momentary action OFFSET pushbuttons allow the user to increase (+) or decrease (-) an internal
offset voltage that is applied when the instrument is in the OPERATE mode. The indication displayed on
the meter (or output at the rear panel) is the sum of the input voltage and the displayed (LCD) value of
offset voltage. The offset voltage can be varied from -30,000.00 μV to + 30,000.00 μV in 0.01 μV steps.
Each digit within the offset voltage display is adjusted up or down independently.
The digit to be adjusted is indicated by an underscore (e.g. 03,000.00 or 00,300.00). The position of the
underscore is selected using the INPUT OFFSET control while the padlock icon () is displayed to the left
of the control. Depressing and holding one of the OFFSET pushbuttons allows continuous movement of the
selected OFFSET voltage digit.
NOTE: Incrementing or decrementing a position within the displayed OFFSET voltage causes a carry to
higher order or lower order digit as appropriate. Depressing both OFFSET pushbuttons simultaneously
resets the offset to 00,000.00 μV.
NOTE: Each range has a maximum permissible offset. Exceeding this offset produces no further offset and
the μV icon blinks.
OPERATE/ZERO -- Pushbutton
A momentary action pushbutton switch selects the OPERATE (measurement) or ZERO mode. In the ZERO
mode the connection between the HI input terminal and the internal amplifiers is opened, the amplifier
input is shorted to the amplifier common and any OFFSET voltage is removed. When the ZERO mode is
selected, the instrument input impedance setting (as displayed on the LCD) is replaced with ZERO. In the
OPERATE mode the voltage to be measured is applied to the input amplifier and the displayed/output
voltage is the sum of the input voltage and the indicated OFFSET voltage.
NOTE: This is NOT the button used to zero the meter.
INPUT/MΩ-- Pushbutton
The INPUT / MΩmomentary action pushbutton allows the user to select the value of resistance present
between the HI and LO input terminals. By successively depressing the momentary INPUT/MΩpushbutton
increments through: 1 MΩ, 10 MΩ, 100 MΩand 1 GΩfor ranges 100nV through 1mV, 10MΩ, 100MΩ,
from 3mV through 300V ranges 100MΩ1,000 V range.
NOTE: This button is not active when OPERATE/ZERO button is set to ZERO.
INPUT OFFSET -- Rotary Control/Pushbutton
This is a multi-function button and should be thoroughly understood prior to operating any other controls
on the AVM-2000.
The INPUT OFFSET rotary control is a rotary encoder that, when enabled by momentarily depressing the
control, allows the user to perform a number of zeroing functions. When the instrument is first initialized,
the control is locked. This is shown by a (a padlock icon) adjacent to the control in the LCD. Depressing
the control once changes the padlock icon to V and depressing the control again changes the icon to I.
When V is displayed the control allows the user to fine tune the current range and mode zero position.
Turning the control clockwise moves the meter upscale and turning the control counterclockwise moves
the meter downscale. The control has a range of approximately ± full scale. The zero adjustment setting is
stored at anytime a range, zero/operate or input impedance change occurs or if the control’s position is
reset to the center or neutral position. The user can reset the control to the center (neutral—i.e. no offset)
position by depressing and holding the control depressed for 5 seconds.

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Section IV – Operating Instructions
When I is displayed, the control allows the user to inject currents of ± 2.5 nA into the input amplifier and
its driving source. This adjustment allows the user to offset any natural instrument and/or measurement
bias currents flowing through driving impedances (causing an offset voltage). Turning the control
clockwise injects a positive current and counterclockwise injects a negative current. Holding the control
depressed for 5 seconds or longer resets the offset current to 0.
NOTE: The level of injected offset current does NOT change as ranges are changed; thus, the input offset
current need only be set once; however, the offset current returns to zero when the instrument power is
turned off.
NOTE: When nulling input bias currents, the user may find using a 100kΩlow-noise resistor or a low-noise
resistor value approximating the source impedance of the device connected between the HI and LO input
terminals is beneficial. When using a 100 kΩresistor, the 30 μV range is a good choice as a starting point.
The 30 μV range and a 100 kΩresistance shows input bias currents of ± 300 pA (full scale) and allows
nulling these input bias currents to substantially less than 1 pA. If the initial indication is off scale, change
the range to 100 μV and then downrange to 30 μV. Alternatively, the 1 MΩinput impedance selection may
be used.
Once the range is zeroed or a desired level of input offset current is selected, the INPUT OFFSET control
may be locked (by depressing the control until the padlock icon is displayed). This prevents further
adjustment of the range zero function or input offset current. The control’s locked/unlocked status is
shown in an adjacent area of the status LCD. A(closed padlock) indicates locked status. Either V or I
indicate unlocked status.
NOTE: with the padlock displayed, adjusting the INPUT OFFSET control allows the user to select which
digit of the OFFSET voltage responds to the OFFSET up and down pushbuttons. An underscore is displayed
under the selected digit (e.g. 03,000.00 or 00,300.00).
OUTPUT LEVEL -- Rotary Control/Pushbutton
This is a multi-function button and should be thoroughly The OUTPUT LEVEL rotary control is a rotary
encoder that allows the user to adjust the ISOLATED OUTPUT level. The range of this control allows the
user to adjust the ISOLATED OUTPUT voltage from ± 0.5 volt to ± 1.5 volt when the meter is deflected to
full scale. The OUTPUT LEVEL control also serves to set the ISOLATED OUTPUT zero voltage when in Setup
mode. The OUTPUT LEVEL control is unlocked or locked by depressing the control once. The control’s
locked/unlocked status is shown in an adjacent area of the LCD. A (closed padlock) indicates locked
status.
OVER VOLTAGE
If a potentially harmful over voltage exists at the instrument’s input amplifier, the Over Voltage circuit is
activated. Once activated, the instrument is disconnected from the input terminals and an over voltage
status is shown on the LCD.
NOTE: The Over Voltage only operates when the instrument Range is 1 mV or below unless an extreme
over voltage occurs (> 1,300 V) on the 3 mV and above ranges—such voltages are likely to damage the
instrument.
When an over voltage condition occurs, the first step is to remove the source of input over voltage. After
the over voltage source is cleared, depressing the OPERATE/ZERO pushbutton once returns the instrument
to operation in the ZERO mode. Depressing the OPERATE /ZERO pushbutton once again returns the
instrument to the OPERATE mode.

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4-5
Section IV – Operating Instructions
WARNING: FAILURE TO REMOVE THE SOURCE OF INPUT OVER VOLTAGE BEFORE RESTORING NORMAL
INSTRUMENT OPERATION MAY CAUSE SERIOUS DAMAGE TO THE INSTRUMENT!
NOTE: Although the over voltage circuits protect the instrument from substantial excessive voltages at its
inputs, it cannot protect the instrument against damage from extremely high voltage spikes that can occur
when the over voltage condition is transient in nature and the voltage spikes are very high due to
inductive spiking. For this reason, great care should be taken when using the instrument in high-
sensitivity modes (especially on ranges of 1 mV and lower) with very high measurement differential
voltages.
Normal Operation
Normal calibration laboratory practice dictates that the environment should be closely controlled. This will
minimize errors introduced by temperature and humidity changes. A nominal temperature of +20°C
provides a good working condition. A tolerance of ±5°C gives allowable temperature spread. Controlled
temperatures also stabilize the aging process of the standards.