Description
Dr. Schneider LS-385 Surface Resistivity Meter
Surface Resistivity and Surface to Ground can be conveniently measured in accordance with Standard D257.
This Surface Resistivity Meter LS-385 with probes is a wide-range, battery operated, portable instrument for measuring surface resistivity of virtually any flat surface.
In the circuit industry, products such as packaging materials, component storage bags and trays, work bench surfaces, table and floor mats, conveyor belts, etc., have resistance values which need to conform to stringent specifications.
Moreover, these values are expected to fall within specified limits.
Surface resistivity meter can play a vital role in monitoring and checking the resistivity characteristics of the above items.
It also has unique additional feature of surface-to-ground measurement capability wherein the resistivity differential between any surface and any chosen ground can be determined.
Color-coded LEDs conveniently indicate conductive, dissipative and insulative values from 103 to 1012 Ω/square.
What kind of unit is Ω/square ?
Surface resistivity is measured in ohms per square. Ohms is unit of resistance, but what about square?
Engineers know that you can measure surface resistivity from one point on the surface to another using an ordinary Ohm-meter. Then the units would be Ohm per distance between points or Ω/m.
But this method yields very inconsistent results, especially with surfaces that are not perfectly homogenous.
More consistent results are obtained by measuring the surface resistivity between two bars. For simplicity, two parallel bars of equal length are placed exactly 1 length apart on the surface to be measured.
They form two opposite sides of a square. It does not matter how long the bars are, since the longer bars will be placed proportionally further apart.
The resistance measured between the two bars in Ohms is the resistivity of the surface in Ohms per square.
In the electronics manufacturing and service industry where we need to protect expensive electronic components from ESD damage, ESD Association has set global standards EN 61340-5-1 Protection of electronic devices from electrostatic phenomena for prevention and control of static damage.
Therefore, various clean room products which are supposed to be ESD safe are used during manufacturing, installation, assembly, repair, servicing, transport of printed circuit boards and they need to control the static damage genuinely.
Why we need to test ESD safe products before use?
In the market there are many low priced clean room products available which may not be capable of maintaining the standards set by ESD Association, so it is recommended to test these products if they are ESD safe or not.
All clean room products which are claimed as ESD safe can be checked if they are Conductive, Static Dissipative or Insulative using surface resistivity meter. This meter has three color combinations of LEDs.
Following table shows the reading and light color on the tester
|
Surface |
Light |
Surface Resistivity (Ω/square) |
Result |
|
|
Conductive |
Green |
<105 |
ESD |
Antistatic |
|
Static Dissipative |
Yellow |
105 - 3.5x107 |
||
|
Static Dissipative |
Yellow |
106 - 1011 |
||
|
Insulative |
Red |
1012 |
Non-ESD
|
|
Need for SRM
Surface resistivity, resistance between 2 points, and Surface to Ground can all be conveniently measured in accordance with EOS/ESD Association Standard S4.1
Measurements with built in parallel electrodes or special external probes in the conductive range i.e. up to 105 Ω/square are made at 10 V and all higher values at 100 V.
A separate cord is also provided for surface to ground measurements whereby the resistance differential between any surface and any chosen ground can be determined.
| Specifications | |
| Model | LS-385 |
| Measurement Range | 103 to 1012 Ω/square |
| Measurement Accuracy |
+/- 10% |
|
Measuring Intensity |
10 Orders of Magnitude |
| Indication | By Color-Coded LEDs |
| Excitation Voltage |
9 V |
| Low Battery | Warning at 7.5 V |
| Dimensions |
(L)130 mm x (W)70 mm x (H)25 mm |
| Power Supply |
9 V DC battery |
| Trace-ability | To National Standards |
| Test Actuation | Press to ON Switch |
| Accessories (Included) | 1 m Grounding Cord & Carrying Case |
| Warranty |
12-Months* |
| Calibration |
Recommended every 12 months |
| Conformance |
D257 |
| Weight | 170 g (Including Battery) |
| Country of Origin | China |
| Brand | Dr. Schneider |
| Operation | |
|
1. Power the instrument for use by opening the back cover to install a 9 V battery. 2. For Surface Resistivity Measurement Place the instrument on any surface which has to be tested so that the two sensor electrodes at the bottom of the instrument are in proper contact with the surface and gently press the TEST button on the instrument. The LED which lights up directly gives the surface resistance in Ω/square. 3. For Surface to Ground Measurement Insert the cord supplied with the instrument into the Ground socket on the instrument and connect the other end of the cord to any convenient ground point e.g., Floor mat. Place the meter on the surface to be checked for surface to ground resistance. Next, as usual, press the TEST button and take the resistance reading in Ohms directly from the LED display. |
|
| Important Note | |
|
1. If the ambient air is humid (like in the rainy season), the instrument may not indicate beyond 1012, even when it is not placed on any surface. This is because of the traces of moisture condensing in the instrument body, thereby forming a conductive path between the sensor electrodes. In such conditions, reliable readings can be obtained only if measurements are taken in a humidity-controlled chamber. 2. Because of the ultra-high sensitivity of the instrument, the user is cautioned that when measuring high resistances (109 or greater) external electrostatic and electromagnetic fields may adversely affect its performances and may lead to erroneous reading. When making measurements in this range, it is recommended that the operator step away from the test setup during the measurement time. Similar precautions should be taken to ensure that there is no electrical device or wiring within about 75 cm of the instrument while measurements are being taken. |
|
| Maintenance | |
| Apart from routine battery replacement, as and when indicated by low battery indication, this instrument is designed to be completely maintenance free. Before taking any measurements, ensure that the surface to be tested and the bottom of the instrument including sensor electrodes are clean because any dust or contaminates on either surface will lead to erroneous reading. |
|
| Warranty | |
|
* Warranty is applicable from the date of invoice. Repair warranty only for the instrument. Forward-Reverse transportation cost from our office in Delhi, India will be paid by purchaser of the equipment. Warranty voids in case of liquid damage, physical damage and/or if warranty seal is voided off. |
|
| Package Contents | |
|
Item |
Quantity |
| LS-385 |
1 N |
| Grounding Cord | 1 N |
| Battery |
1 N |