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Static Solutions Inc.
Static Solutions Inc. - Ohm - Stat RT - 1000 Information
7
RT-1000 Question and Answers
1.
Why is it important to measure temperature and humidity ?
Answer-
The humidity and temperature affect the electrical properties of the material being tested. The combination of low humidity
and low temperature will give the highest electrical resistance results or slowest dissipation times. At high humidity a thin layer of
water is condensed or absorbed on or in the material being tested. This is true of hydroscopic additives added to a material to
increase the electrical conductivity which is moisture absorbable. At elevated temperatures the mobility of free electrons is increased
thereby increasing the materials conductivity. This is especially true for carnon black , metallic oxides, metals, and other materials
added to a material which must be mobile or in close proximity. When the material is at a lower temperature built in stresses occur
which might increase the resistance due to increased distance between the conductive additives. Thus, humidity and temperature
must be known. It is possible to test or manufacture a material at high humidities and pass all the test specifications. But, when the
customer receives the material and uses it at a lower humidities, or temperature the material fails to pass the specifications.
Thus,causing rejects and loss of product. Another reason why one must measure and record this data is that ANSI/ESD Association
and European CECC recognizes the environmental affects and specifies in their standards that they measured and recorded.
For example both ESD S4.1 ESD Protective Worksurfaces section 6.2.4 and ESD S7.1-1994 Resistaive Characterization of Materials
Floor Materials sections 5.2.4 and 5.3.3 “Also report temperature and relative humidity at the time of testing”. ANSI/EOS/ESD-
S11.11-1993 Surface resistance measurement of Static Dissipative Planar Materials section 11.0 B. “report the conditioning period,
relative humidity, and temeperature.”
All parties must test and record the data using the same parameters in order to avoid problems. The manufacturer, distributor, sales
person, and customer must understand the environmental humidity and temperature parameters in order to not accept out of
specification materials or reject in specification materials. Both of these situations will cost money to rectify.
2.
Why and when do you test at either 10 volts or 100 volts ?
Answer:
In previous years people desiring to measure resistivity or resistance had to follow either the ASTM- D 264, ASTM- 991,
or NFPA 56A or NFPA 99. In these procedures people had to test at either 500 or 1000 volts. This caused concern regarding safety
to the person doing the tests. People wanting a smaller low cost meter measured the surface at 9 volts. 9 volts WILL NOT give the
accuracy that you need to perform the tests. In addition a 9 volt meter does not conform to EOS and 20/20 specifications.. At 9 volts
it is impossible to achieve accuracy at values higher than 10
7
ohms. These specifications require to measure both the humidity and
temperature. What resulted was confusion. Everybody was doing their own tests.Finally the ESD Association got together to
standardize the test procedures with all the organizations.
What was decided was at values higher than 10
6
ohms/square one must test at a constant 100 volts. At values lower than
10
6
ohms/sq. one must use 10 volts. This is explained in ANSI/EOS/ESD standards -S4.1,S7.1 and S11.11
3.
Why is an alpha-numeric superior than an analog or LED display ?
Answer
: Have you ever tried to interpret a value on an analog scale at high values, especially if your age is over 50 years old and
need glasses. It is very difficult to see and read !! The problem with LED displays are that it is difficult to determine where you are
on a specific decade. The advantage of a digital alpha-numeric display is that you can observe and track trends of a material over
time and it is easy to read and interpret.
4.
With the meter can you use rechargeable batteries ?
Answer
: Yes, the adapter is both a converter and a in meter re-charger. It is recommended to use only a rechargeable battery with
the power supply and do not use the power supply when using a conventional alkaline battery. It might cause leakage .
5.
Can you use the meter without the external probes ?
Answer
: Yes. The meter can be used with the built in parallel probes attached at the bottom the meter. This resistivity reading is in
ohms/square. This is a fast and quick way to measure the surface resistivity. This is a good simulation of the ASTM D-257 test
method with the meter power switch activated at a force of 5 pounds of pressure onto the built in parallel probes. Always remove
the coil cords from the meter when not using the external probes or when you use the bottom parallel resistivity probes. Because
there is no such thing as surface resistivity of two layer materials one can do a quick test for immediate evaluations.