WPI ISO-DAM User manual

World Precision Instruments, Inc.
USA
International Trade Center, 175 Sarasota Center Blvd., Sarasota FL 34240-9258
Tel: [phone] • Fax: [phone] • E-mail: [e-mail]
UK
Astonbury Farm Business Centre • Aston, Stevenage, Hertfordshire SG2 7EG
Tel: [phone] • Fax: [phone] • E-mail: [email protected]
Germany
Liegnitzer Str. 15, D-10999 Berlin
Tel: [phone] • Fax: [phone] • E-mail: [e-mail]
Internet
www.wpiinc.com • www.wpi-medical.com
www.nitricoxide.net •www.pipetter.com
ISO-DAM
Isolated low-noise preamplifier
World Precision Instruments
INSTRUCTION MANUAL
Serial No._____________________
031507
www.wpiinc.com

ISO-DAM

ISO-DAM
6 WORLD PRECISION INSTRUMENTS
Copyright © 2002 by World Precision Instruments, Inc. All rights reserved. No part of this publication
may be reproduced or translated into any language, in any form, without prior written permission of
World Precision Instruments, Inc.
Contents
Introduction..............................................................................................................................1
Noise and Interference..........................................................................................................2
Quick Test .................................................................................................................................2
Input Connection ....................................................................................................................2
DC Bal........................................................................................................................................3
Output........................................................................................................................................3
Filters..........................................................................................................................................3
DC/DC Offset...........................................................................................................................3
Charge .......................................................................................................................................3
Power Adapter.........................................................................................................................4
Specifications...........................................................................................................................4
Warranty ...................................................................................................................................5

ISO-DAM
* Electrodes, batteries and other consumable parts are warranted for 30 days only from the date on which the
customer receives these items.
WORLD PRECISION INSTRUMENTS 5
Warranty
WPI (World Precision Instruments, Inc.) warrants to the original purchaser that this equipment, including its
components and parts, shall be free from defects in material and workmanship for a period of one year*
from the date of receipt. WPI’s obligation under this warranty shall be limited to repair or replacement, at
WPI’s option, of the equipment or defective components or parts upon receipt thereof f.o.b. WPI, Sarasota,
Florida U.S.A. Return of a repaired instrument shall be f.o.b. Sarasota.
The above warranty is contingent upon normal usage and does not cover products which have been
modified without WPI’s approval or which have been subjected to unusual physical or electrical stress or
on which the original identification marks have been removed or altered. The above warranty will not
apply if adjustment, repair or parts replacement is required because of accident, neglect, misuse, failure of
electric power, air conditioning, humidity control, or causes other than normal and ordinary usage.
To the extent that any of its equipment is furnished by a manufacturer other than WPI, the foregoing
warranty shall be applicable only to the extent of the warranty furnished by such other manufacturer. This
warranty will not apply to appearance terms, such as knobs, handles, dials or the like.
WPI makes no warranty of any kind, express or implied or statutory, including without limitation any
warranties of merchantability and/or fitness for a particular purpose. WPI shall not be liable for any
damages, whether direct, indirect, special or consequential arising from a failure of this product to operate
in the manner desired by the user. WPI shall not be liable for any damage to data or property that may be
caused directly or indirectly by use of this product.
Claims and Returns
Inspect all shipments upon receipt. Missing cartons or obvious damage to cartons should be noted on the
delivery receipt before signing. Concealed loss or damage should be reported at once to the carrier and an
inspection requested. All claims for shortage or damage must be made within ten (10) days after receipt
of shipment. Claims for lost shipments must be made within thirty (30) days of receipt of invoice or other
notification of shipment. Please save damaged or pilfered cartons until claim is settled. In some instances,
photographic documentation may be required. Some items are time-sensitive; WPI assumes no extended
warranty or any liability for use beyond the date specified on the container
Do not return any goods to us without obtaining prior approval and instructions from our Returns
Department. Goods returned (unauthorized) by collect freight may be refused. Goods accepted for
restocking will be exchanged or credited to your WPI account. Goods returned which were ordered by
customers in error are subject to a 25% restocking charge. Equipment which was built as a special order
cannot be returned.
Repairs
Contact our Customer Service Department for assistance in the repair of apparatus. Do not return goods
until instructions have been received. Returned items must be securely packed to prevent further damage
in transit. The Customer is responsible for paying shipping expenses, including adequate insurance on
all items returned for repairs. Identification of the item(s) by model number, name, as well as complete
description of the difficulties experienced should be written on the repair purchase order and on a tag
attached to the item.

ISO-DAM
supply. With the Power switch in the OFF/CHARGE position, the red lamp above the
switch will light while the batteries are charging. When depleted, batteries can usually
be recharged in 12 to 14 hours. They should not be damaged by charging for longer
periods.
Power Adapter
The wall power adapter (power supply) converts mains alternating current to 12 volts DC
to power ISO-DAM. Note that the power receptacle on top of the unit is dual. Thus, using
a jumper cable (provided), up to four ISO-DAM amplifiers can be operated from one
power adapter. Jumper cables are supplied for each amplifier so that ISO-DAMs can be
multiply connected to 12 volt DC power. The user may also substitute a 12 volt storage
battery as a power source rather than line power if desired.
Specifications
Voltage Gain ×10, ×100, ×1000, ×10,000
Input R to Gnd, each input > 1012 Ohms
Input R, between Inputs > 1012 Ohms
Amp Noise, input shorted < 0.4 µV rms (1 Hz-100 Hz),
< 2 µV rms (1 Hz-10 kHz)
Bandwidth DC to 10 kHz
Filter, low pass 0.1, 0.2, 0.5, 1, 3, 10 kHz
Filter, high pass 0.1, 1, 10, 300 Hz
Input Offset V. Adjust. ± 100 mV
Common Mode Rejection > 100 dB @ 50/60 Hz
Output Voltage Swing ± 5 Volts
Output Resistance 220 Ω
Power Adapter 115 V 60 Hz or
230 V 50 Hz to 12 V DC (user specifies)
Dimensions 8 ×4 ×1.75 in. (20.3 ×10.2 ×4.4 cm)
Weight 1.5 lb (0.7 kg) approx.
Shipping Weight 3.5 lb (1.6 kg)
4 WORLD PRECISION INSTRUMENTS
Introduction
The ISO-DAM preamplifier is photoelectrically isolated from earth ground. No significant
current can flow from input terminals of the instrument to ground. The instrument is
intrinsically safe and cannot cause any electrical stimulus or shock to the subject. ISO-
DAM’s small case allows the instrument to be placed close to the site of measurement.
ISO-DAMs can be stacked in groups of four in a convenient 19-in. rack mount.
The input stage of ISO-DAM is battery powered by two long-lived miniature Ni-Cd
batteries and has no electrical connection to the AC power circuit ground. This isolation
is achieved by photoelectric coupling. Isolated preamplification has several important
advantages over non-isolated amplifiers.
WORLD PRECISION INSTRUMENTS 1
Faraday ground
–
BLACK
+
RED
BRAID
(Ground Reference)

ISO-DAM
1. Amplifier input connections are completely disconnected from the Power (Mains)
ground.
2. No significant current can flow from the preamplifier input terminals to ground.
Therefore, input connectors are intrinsically safe and cannot cause electrical shock at the
site of measurement.
The wall power supply unit provides DC power to the post-isolation output stage of the
amplifier. The power supply also provides DC current to charge the isolated front end
batteries when the power switch is turned off. Estimated battery operating time between
charges is 160 hours. When the ISO-DAM is in use, keep the wall power (AC adapter)
plugged in in order to supply DC power to the output stage of the amplifier.
Noise and Interference
The bane of low level bioelectric recording is electrical noise and interference originating
from the current and voltage in the power mains and room lighting power. Every
high amplification preamplifier is subject to this handicap; particularly when using
microelectrodes. It is therefore recommended that all input leads be shielded and
the preparation connected to earth (ground). Often, it will be necessary to enclose
the preparation and electrode lead wires in a Faraday cage or shield to reduce mains
induction to sufficiently low levels. Often it will be beneficial to extinguish overhead
fluorescent lighting as well.
Quick Test
To determine if the preamplifier is operational, switch the Low Filter switch to GND and
the Gain switch to ×10. With the power supply connected, the Off/Charge lamp should
be lit. Turn the Power switch to On. The On lamp should light. The two red Output lamps
should easily switch between the - and + lamps as the Zero knob is rotated.
Input Connection
The input connector of the preamplifier is a single 3-pin socket (pin 1 is positive [+],
pin 2 is negative [–], pin 3 is ground). The input plug has a shielded cable (1.5 m)
terminating in red, black, white and green wires. The red wire is positive (non-inverting);
the black wire is negative (inverting); white and green wires are not used. Ground
Reference is the copper braid (pin 3). The Faraday ground socket, located to the right of
the input socket, is a 3 mm banana-type socket (one banana plug is also included with
the instrument). The user should connect this receptacle to the system ground point (i.e.,
that point where the recording site is connected to Power (Mains) ground. The subject or
2 WORLD PRECISION INSTRUMENTS
preparation should also be connected to ground. Input protective devices limit the input
differential signal from exceeding ± 3 volts.
DC Bal.
The DC Bal. (balance) potentiometer allows the user to adjust Gain switch position
stability. The potentiometer is accessible with a small screwdriver hole on the front
panel. To adjust the DC Bal. first perform the QUICK TEST procedure as outlined above.
Using an oscilloscope or recorder connected to the Output connector, adjust the Zero
knob so that the output trace on the recorder is near the zero volt level. Rotate the GAIN
selector switch from ¥10 to ¥10000. If the baseline moves, readjust the DC Balance pot
at the ¥10000 setting with a small screwdriver until the baseline returns its prior setting.
The baseline should not deflect appreciably when the GAIN switch is reduced to lower
values.
Output
The maximum Output signal from the amplifier is ± 5 volts.
Filters
ISO-DAM provides selected filtering at both the high and low ends of its frequency
spectrum. The Low Filter (“high-pass”) 3 dB cut-off points are 0.1, 1, 10 and 300 Hz,
respectively. The High Filter (“low-pass”) cut-off frequencies range from 100 Hz to 10 kHz.
For example, typical settings recommended for ECG and EEG would be Low Filter at 0.1
Hz and the High Filter at 0.1 kHz (100 Hz).
DC/DC Offset
When operating the ISO-DAM as a DC amplifier, the user may require a DC offset
potential with which to compensate any existing DC voltage from the recording site. The
DC Offset knob can provide 0 to 100 millivolts of either polarity with which to reduce
(null) the net input to zero volts. This becomes increasingly necessary if high gains are to
be used with DC amplification. The toggle switch below the DC Offset knob selects the
polarity of the offset voltage. If offset adjustment is not required, the toggle switch is kept
in the Off position.
Charge
Insure that the Nickel-Cadmium batteries are fully charged before using the amplifier.
Connect the receptacle on the top side of the ISO-DAM case to the DC wall power
WORLD PRECISION INSTRUMENTS 3