ETS 871 User manual

WIDE RANGE RESISTANCE METER
Model 871
Operating Instructions
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IMPORTANT
SAFETY INSTRUCTIONS
(Equipment without HV)
The equipment described in this Manual is designed and manufactured to operate within
defined design limits. Any misuse may result in electric shock or fire. To prevent the equipment
from being damaged, the following rules should be observed for installation, use and
maintenance. Read the following safety instructions before operating the equipment. Retain
these instructions in a safe place for future reference.
POWER
POWER CORD: Use only the power cord specified for this instrument and certified for the
country of use. If the power (mains) plug is replaced, follow the wiring connections specified
for the country of use. When installing or removing the power plug hold the plug, not the
cord.
The power cord provided is equipped with a 3-prong grounded plug (a plug with a third
grounding pin). This is both a safety feature to avoid electrical shock and a requirement
for correct equipment operation. If the outlet to be used does not accommodate the 3-prong
plug, either change the outlet or use a grounding adapter.
FUSES: Replace fuses only with those having the required current rating, voltage and
specified type such as normal blow, time delay, etc. DO NOT use makeshift fuses or short
the fuse holder. This could cause a shock or fire hazard or severely damage the
equipment.
POWER LINE VOLTAGE (MAINS): If the line (mains) voltage is changed or isolated by an
autotransformer the common terminal must be connected to the ground (earth) terminal of
the power source.
OPERATION
DO NOT OPERATE WITH COVERS OR PANELS REMOVED. Voltages inside the
equipment consist of line (mains) that can be anywhere from 100-240VAC, 50/60Hz and in
some equipment, test voltages up to 500VDC.
DO NOT OPERATE WITH SUSPECTED EQUIPMENT FAILURES. If any odor or smoke
becomes apparent turn off the equipment and unplug it immediately. Failure to do so may
result in electrical shock, fire or permanent damage to the equipment. Contact the factory
for further instructions.
DO NOT OPERATE IN WET/DAMP CONDITIONS: If water or other liquid penetrates the
equipment, unplug the power cord and contact the factory for further instructions.
Continuous use in this case may result in electrical shock or fire.

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DO NOT OPERATE IN HIGH HUMIDITY: Operating the equipment in high humidity
conditions will cause deteriation in performance, system failure, or present a shock or fire
hazard. Contact the factory for further instructions.
DO NOT OPERATE IN AREAS WITH HEAVY DUST: Operating the equipment in high
dust conditions will cause deteriation in performance, system failure, or present a shock or
fire hazard. Contact the factory for further instructions.
DO NOT OPERATE IN AN EXPLOSIVE ATMOSPHERE: Operating the equipment in the
presence of flammable gases or fumes constitutes a definite safety hazard. For
equipment designed to operate in such environments the proper safety devices must be
used such as dry air or inert gas purge, intrinsic safe barriers and/or explosion-proof
enclosures.
DOT NOT USE IN ANY MANNER NOT SPECIFIED OR APPROVED BY THE
MANUFACTURER: Unapproved use may result in damage to the equipment or present an
electrical shock or fire hazard.
MAINTENANCE and SERVICE
CLEANING: Keep surfaces clean and free from dust or other contaminants. Such
contaminants can have an adverse affect on system performance or result in electrical
shock or fire. To clean use a damp cloth then let dry before use. Do not use detergent,
alcohol or antistatic cleaner as these products may have an adverse affect on
system performance.
SERVICE: Do not attempt to repair or service the instrument yourself unless
instructed by the factory to do so. Opening or removing the covers may expose you to
high voltages, charged capacitors, electric shock and other hazards. If service or repair is
required, contact the factory.

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1.0 INTRODUCTION
Many applications, especially, in the area of static control require the measurement of
the resistance characteristics of packaging, materials, work surfaces, flooring plus any
object where the build-up and dissipation of static charge is of concern. Some materials
are nonlinear and have a measured resistance that is a function of test voltage. Various
specifications including those written by the ESDA (STM 4.1, 11.11, 11.12, 11.13, etc.),
ASTM (D257, 4496, F150 etc.), EIA, SAE (J1645, etc.), NFPA (77, 99 etc) military (MIL
PRF 81705 etc.) plus many international documents (IEC, CECC etc) specify or use test
voltages of 10 and 100 Volts.
Specifications such as ASTM F-150, NFPA 99 and certain DOD Standards require test
voltages of 500 volts. Normally, higher test voltages will generally result in lower
resistance readings. Hence, an acceptable reading utilizing 10 or 100 volts will typically
meet those resistance requirements specified at higher voltages where resistance
below a specified value is required. However, when 500 V is required to ensure that
resistance does not drop below a specified value for safety purposes, then a 500 V
instrument MUST be used.
The ETS Model 871, shown in Figure 1.0-1 is an accurate, battery/AC powered,
microcomputer-based instrument that meets the requirements for measuring resistance
from 102 to >1012 Ohms using user selectable regulated test voltages of 10 or 100V.
The included external universal voltage power module allows continuous operation of
the Model 871 without draining the batteries.
Figure 1.0-1: Model 871
2.0 DESCRIPTION
The Model 871 Wide Range Resistance Meter is an accurate, easy to use laboratory
grade, microprocessor-based, autoranging instrument. The Meter is activated when the
MEASURE select paddle switch is placed in either the Ve=10V or 100V position.

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Optionally, a foot switch enables remote activation of the instrument. This function is
very convenient when measurements are being performed in a test chamber. The
included universal power module (90-265VAC, 50/60Hz) permits continuous operation
of the Meter without draining the batteries. The 2-line alphanumeric LCD readout
displays the measured resistance on the top line and the test voltage (Ve=10 or 100V)
on the bottom line. Resistance is displayed in engineering units (ex: 6.35e+8 =
6.35x108) plus UNDERSCALE and OVERSCALE indication. The lowest measurable
resistance is 100 at 10V and 10 kat 100V. The highest measurable resistance is
approximately 5 x109at 10V and 5.5x1012 at 100V. Measurement accuracy is
better than 2% over the entire measurement range.
Electrification time is a function of the test lead, probe and sample capacitance.
Generally, probes with 36” (1m) cables will require an electrification time of
approximately 60 seconds to achieve maximum reading. External probes are connected
to the Model 871 via standard banana jacks located on the rear of the instrument. Refer
to available ETS Series 800 Resistance/Resistivity Probes literature sheets for probes
to meet virtually any surface, volume (solids, liquids and powders) and point-to-point
resistance measurement requirement. Other probes having standard banana plug leads
may also be used.
Figure 2.0-1 shows the rear panel of the Model 871.
Figure 2.0-1: Model 871 Rear Panel
When battery voltage is low the display automatically displays Low Battery.

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3.0 OPERATION
3.1 Hook-up
Connect the probe to the input banana jacks located on the rear panel as shown
in Figures 3.1-1 to 3.1-5 for measuring surface, point-point and point to ground
(RTG) resistance. The Red jack is Ve (test voltage), the Black Jack is SENSE
(measuring input) and the Green jack is probe ground. For greater measurement
stability at the higher resistance ranges connect the Green cable provided to the
GND jack and house electrical ground. If the power module is being used
connect it to the EXT PWR jack. NOTE: When the using the power module the
Meter MUST be connected to house electrical ground. Otherwise, incorrect
measurements may be obtained.
Figure 3.1-1: Connection for measuring surface resistance per
ESDA STM 11.11
Figure 3.1-2: Connection for measuring volume resistance per
ESDA STM 11.12

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Figure 3.1-3: Connection for measuring 2-point resistance per
ESDA STM 11.13
Figure 3.1-4: Connection for measuring point-to-point resistance and RTG per
ESDA STM 4.1

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Figure 3.1-5: Connection for measuring point-to-point resistance per SAE J1645
When using battery power the display will indicate only the alphanumeric text.
When the power module is used the display back light will automatically be
activated, enhancing the readout.
3.2 Taking Measurements
Turn on the Meter and place the MEASURE paddle switch in the STANDBY
(center) position. The display will read STANDBY. Place or attach the probe(s)
as indicated above on or to the object being measured. If the resistance of the
sample is unknown, place the MEASURE switch in the Ve=10V position. Wait at
least 5 seconds or until a stable reading is obtained. If the measured resistance
is greater than 1x106 Ohms switch to Ve=100V and take a reading.
Measurements above or below the measurement range of the Meter will be
displayed as UNDERSCALE or OVERSCALE. To repeat the measurement it is
best to first go back to STANDBY to bleed off any voltage that may remain on the
electrodes. If measuring in accordance with an established test method, then
follow the procedure specified. When applicable, the resistance measurement
can be converted to resistivity by multiplying the measured resistance by the
appropriate probe configurations. For the ETS Model 803B Surface/Volume
Resistance Probe multiply the measured surface resistance by 10 (s=10Rm
Ohms/sq).
To make a volume resistance measurement, connect the conductive test bed to
the Veoutput (Red). Place the planar material to be tested on the conductive
plate and then place the probe on top of the material. Select the desired test
voltage by placing the paddle switch it the upper (Ve= 10V) or lower position (Ve
= 100V) until a stable reading is obtained. To convert a volume resistance
measurement to volume resistivity, multiply the reading by 31.7 (the area a 2.5”
electrode in cm2) and divide by the thickness of the sample in cm (v=31.7/t
Ohms-cm). If the center electrode of a Model 803B is used (STM 11.12) then use
7.1 instead of 31.7.

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To measure pt-to-pt resistance or RTG plug an ETS Model 850, 845 or
equivalent probe into the Ve(Red) jack. To measure pt-pt, place the probes onto
the surface to be measured. To measure RTG connect the supplied red wire
from the Vejack to the desired ground point using either the banana plug or the
alligator clip adapter supplied. Wait at least 5 seconds (or allow enough time for
electrification) before reading the Meter. Since the 5 pound probe weight
provides the specified contact pressure, no additional pressure should have to be
applied.
For all other measurements refer to the test method referenced for the
application such as ESDA STM11.13, SAE J1645, ASTM D257 etc.
The effects of electrification time should also be observed when making pt-pt and
RTG measurements, particularly if the resistance range is above 1010 ohms.
4.0 MEASUREMENT CONSIDERATIONS
4.1
Resistance
For most film and foam materials the standard 5 pound weight of the Model
803B Resistance Probe is sufficient for the electrodes to make total contact with
the material surface. However, for rigid materials such as work surfaces, plastics,
cardboard, etc, additional force, which will have to be determined by the user,
may have to be applied to the Probe to ensure total electrode contact.
Microscopically, these surfaces are generally not smooth and are uneven as
illustrated in Figure 4.1-1.
Figure 4.1-1: Microscopic Electrode/Rigid Surface Contact
In most cases the application of additional pressure will cause the measured
resistance reading to decrease. This is a result of both lower contact resistance
and total electrode/surface contact area (greater number of parallel resistance
paths). Optimum contact pressure is obtained when the resistance measurement
is stable.

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Another area that should be considered when attempting to measure surface
resistance is the composition of the material being evaluated. ANSI/ASTM D-
257, a widely used test standard, is specified for homogeneous, insulating
material.
However, many materials are either not homogeneous, relatively conductive and
in the case of some composite material, nonlinear. For these materials a surface
resistance measurement in accordance with ESD STM11.11 must be used.
For example, the surface resistance of bulk-loaded materials have relatively low
volume resistance and cannot easily be measured because the volume and
surface resistance become part of the measurement. The current path between
the electrodes is not only across the top surface but also through the material.
Similarly, the surface resistance of materials that are coated with, or laminated
to, a conductive surface must also be measured using STM11.11. The surface
resistance may actually be very high, but the volume resistance may be
significantly lower. Therefore, the measured resistance may be that of the
surface resistance path between the electrodes in parallel with the series
combination of the two volume conductive paths and the conductive layer as
shown in Figure 4.1-2.
4.1-2: Multiple resistance paths of laminated material
Composite materials are very difficult to measure. They usually consist of a
plastic resin filler with very high resistance properties loaded with a small
percentage of a conductive material such as carbon powder, fibers or utilize
nanotube technology. When molded these parts exhibit either conductive or
static dissipative properties as defined in the ESD ADV1.0: Glossary of Terms.
These materials have bulk resistance properties verses the surface only
resistance properties found in other ESD materials. When a voltage is applied
either across or through the material the dielectric of the filler breaks down and
current flows from particle to particle. As the loading of the conductive medium
decreases there is greater distance between particles that require a higher
voltage to break down the increased dielectric. At some point, once a higher

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voltage is applied to establish continuity the resistance path created may become
altered permanently. It should be noted that loaded thermoplastic materials are
only effective in reducing the upper resistance limit to approximately 108Ohms.
Another characteristic of loaded thermoplastic materials that affects the
resistance measurement is the microscopic insulative layer that develops on the
surface of the molded part. The dielectric of this layer must be broken down
before a resistance measurement can be made. Once this occurs the actual
resistance of the part may be lower than the measuring range of the
instrumentation used.
Essentially, these materials are non-linear and voltage dependent. Different test
voltages will give different results. Even the series resistor incorporated in
virtually all resistance meters vary from meter to meter and can cause
measurement variations. When measuring these materials the initial
measurement should be always be made first at Ve= 10V then at 100V.
Another very important consideration in measuring surface resistance is the time
of electrification. This is the time for the effective capacitance of the material plus
the measuring probe and associated cables to charge up. At this time, the
current flow through the material reaches steady state and its flow is then a
function of only the resistance of the material.
Effective material capacitance is generally quite low. For low resistance
materials, the RC time constant, , is very short. On the other hand, for very high
resistance materials the time constant can become quite long.
Resistances that are measured before the full time of electrification has occurred
will appear to be lower than the actual resistance of the surface. This difference
can be several orders of magnitude. ASTM D 257 recommends a time of
electrification of 60 seconds, but in many measurements a shorter time may be
used or a longer time may be required. Typically for small sample specimens
with resistances less than 1012 ohms, the of 5 to 30 second electrification time is
sufficient. On the other hand, large surfaces such as table tops, floors etc. the
capacitance is relatively large and 60 seconds may not be long enough. Here,
the user may either wait for complete electrification to obtain a true resistance
measurement or specify the measurement at the 60 second electrification time
point for a relative resistance measurement. A rule of thumb, “When in doubt,
allow more rather than less time!”
4.2 RESISTANCE CHARACTERIZATION
Over the years many different resistivity or resistance values have been assigned
to designate the various classifications of ESD material. Surface resistivity per
ASTM D257 was the most common specification used to classify materials.

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However, this specification is for insulating materials and when the bulk
characteristics of the material come into play significant errors are introduced.
This became apparent during packaging material specification development
approximately 15 years ago. It was found that by specifying all test parameters
measurement variations between laboratories testing the same material was
reduced from 3 orders of magnitude to better than one-half order of magnitude.
Since all measurement parameters were now specified it was no longer
necessary to specify the measured resistance readings in Ohms/square since
the electrode configuration factor was no longer required. Therefore, all ESD
resistance values are now specified in Ohms. This is covered in ESDS STM
11.11, 11.12 and 11.13 for surface, volume resistance and 2-point
measurements respectively.
Currently ESD materials are classified as follows:
Conductive Dissipative Insulative
Surface <104104to <1011 1011 Ohms
Volume same
Materials with bulk resistance characteristics can also be classified by specifying
its volume resistivity. This is simply done by multiplying the measured resistance
by the area of the measuring electrode or material surface, whichever is smaller,
and divided by the thickness. All values are in cm giving a volume resistivity in
Ohms-cm. To convert to Ohms-meter, multiply by 100.
Increasing or decreasing the thickness of the material will also change the actual
resistance of the part with a specified volume resistivity. This is a common
technique used in ESD products to achieve a particular resistance. It is the actual
resistance of the part, not its resistivity that determines how a part dissipates a
static charge.
While the above resistance classifications were initially developed for ESD
packaging materials many specifications used for other applications that specify
material resistance/resistivity refer to these resistance limits.
It should be noted that the resistance/resistivity property of material does not
predict whether the material will be low charging (antistatic) or not.
4.3 Measurement Documentation
When certifying material it is best to do it under controlled environmental
conditions. Since lower humidity can affect the material resistance properties all
certification tests should be prepared and performed at 12% RH and 23C as
specified in ESD STM 11.11 & 11.12. Since current plastics industry
standards specify standard conditions at 50% RH, 23  C certification should
also be performed at these conditions also to allow comparison of existing
data.

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For testing components and assemblies a controlled environment may not be
practical. Under these conditions the humidity and temperature should be
recorded at the time of testing.
The following procedure should be followed when measuring and documenting
resistance measurements:
1. Sample preparation
2. Test instrumentation including setup and system verification tests.
For loaded thermoformed material the test instrumentation, electrodes and
system verification are critical in obtaining multi-lab correlation and must be
specified.
3. A defined electrification period (measuring time).
When measuring very high resistance the RC time constant of the sample
and the instrumentation may require a significant amount of time for the test
voltage to completely develop across the sample. The electrification time may
be different for different instruments. Hence, measuring a known resistor at
the upper limit will enable the user to determine the time it takes to measure
the correct value.
Some materials may exhibit a change in resistance during measurement.
Taking measurements at a fixed time minimizes this problem.
4. Test procedure
The test procedure is extremely important. How the sample is prepared, test
electrodes, how the instrumentation is connected, test voltages used and how
the measurement is taken all affect the ultimate accuracy of the data.
5. Documentation and reporting of data.
Complete documentation of the measurements is essential. The level of data
processing is a function of the end user requirements.
5.0 COMPUTER INTERFACE
The Model 871 has a 9-Pin sub min-D RS232A COMM PORT (Note 1) that provides
real time data through serial communication. A PC will receive data by simply sending
character R (for result) to the device. A simple program must be written by the user in
order to collect data. The data can then be transferred to a spreadsheet or other
program to obtain the desired data logging and/or analysis. To utilize this function
connect a standard 9 Pin sub min-D cable to the serial port of the PC. The serial cable
is the standard 3-wire null connection (2 to 2, 3 to 3 and 5 to 5).

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To collect data without writing a program, standard Hyper Terminal from any windows
operating system can be used. In most computers, to bring up the Hyper Terminal
program click on “Start” (lower left hand corner), select Accessories then
Communications then Hyper Terminal. Double click on exe. Under Name, type in
“ETS871” then click OK. Under “Connect using” (on some older Terminals it is the
“Phone number”) select the correct COMM port, which the supplied cable is connected
to. Set the following properties:
Baud rate: 9600
Data bit: 8
Stop bit: 1
Parity: None
Flow Control: None
For the computer to receive the data, depress “R” to send the command signal to the
ETS871. The ETS 871 sends what is on the liquid crystal display. If the LCD displays
STANDBY,OVERSCALE or UNDERSCALE (Note 2), the unit will send the same
message. However, the actual result will be sent without any decimal point. For
example, if the LCD displays 5.00 e+6 Ω, the ETS 871 will send 500 e+4 to the host
computer instead.
Note 1: Serial communication signals of ETS871 are inverted serial output lines.
RS232A is characterized as a ±5V bipolar signal (as opposed to RS232C at ±12V).
Most PC recognize serial communication level shift below 5V. However, a level shifting
converter such as the MAX232 is required for a PC that can only recognize serial
communication with bipolar signal beyond ±5V.
Note 2: If the “R” command is sent while LCD displays foot sw. to read, the ETS 871
will send the result after the foot switch is pressed.
6.0 MAINTENANCE
The Model 871 has no user serviceable parts except changing the batteries. The
instrument must be returned to ETS for service. Contact ETS Repair/Recalibration
Department at 215-887-2196 to obtain a Return Material Authorization (RMA) for all
warranty, repair and calibration service.
The user can check the calibration of the Meter by measuring the resistance of
precision resistors over the measurement range of the instrument.
To change batteries lift and pull out the battery drawers on the rear of the unit as shown
in Figure 6.0-1. Replace batteries as a pair. Use only 9-Volt alkaline or other high
capacity batteries for best performance.

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Figure 6.0-1: Changing batteries
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7.0 WARRANTY
Limited Warranties. Seller warrants that all goods manufactured and delivered
hereunder shall (a) conform to any samples, drawings, specifications or other written
documents provided to Seller by Buyer, or approved by Buyer to Seller and (b) be free
from all defects in workmanship and material. Buyer’s sole remedy against Seller for
breach of either of the specifically mentioned warranty shall be the repair or
replacement, at Seller’s sole option, of the defective workmanship or material. Seller
expressly disclaims all other warranties, express and/or implied, including but not limited
to those of merchantability and fitness for a particular purpose. In no event shall Seller
be liable, under either warranty or otherwise, to Buyer in excess of the purchase price of
the products paid to Seller by Buyer. In no event shall Seller be liable for any loss or
damage arising directly or indirectly from the use of the product or for consequential or
incidental damages. Seller’s specified warranties will expire and lapse (i) for renewable
items (such as gloves, iris ports and desiccants), sixty (60) days from date of shipment
and (ii) all standard equipment and otherwise nonrenewable items, one year from date
of shipment.