Extech Product Frequently Asked Questions

General Questions

Software communication problems can occur due to a few reasons. Please click on the appropriate troubleshooting guide (link) below for assistance.

Software Trouble Shooting Guide - Com Ports
Software Trouble Shooting Guide - USB Ports

All Extech products are factory calibrated prior to shipment. This calibration is valid for one year. An annual factory calibration is recommended. Extech does not include calibration certificates with our products. NIST calibrations with data can be purchased for an additional charge for most products. To send your meter to be NIST calibrated please contact our return department for a return authorization number and other return information.

All Extech User's Guides can be found on the website. Click on Instruments Division and go to the Product Category List. Click on the category of your instrument and find the specific model you are looking for. Here will be an option to download a PDF of the User's Guide.

Extech meters should be calibrated annually.

Please email your request for a calibration procedure to support@extech.com. Please remember to include the model number of your meter.

Yes, we can cross reference other manufacturer's products to Extech products. Please provide us with the manufacturer's name & model number so that we may recommend an equivalent or better product to fulfill your application needs. Please submit your request to our Tech Support department by email at support@extech.com.

Airflow Meters

The area of the duct needs to first be calculated in order to make CFM & CMM measurements. Please use the following formulas to calculate the area.

Area Formulas

NOTE: Measurements made in inches must be converted to feet or meters before using the above formulae (divide by 144).

Extech does not have an anemometer that can be used in temperature applications above 175oF. The limit is not in the electronics of the meters but in the melting temperature of the plastic being used in the sensors.

The meter will have to be sent in if the vane needs to be replaced as the sensor is calibrated to the meter.

Clamp Meters

Putting the clamp meter around more than one conductor causes the current reading to cancel out. To properly read current, you will need to measure each conductor separately. The easiest way to do this without damaging the power cord is to use a line separator (Extech model 480172).

The most accurate way to measure low current is by putting a multimeter in series with the circuit. However, breaking the circuit may not be possible. Extech carries a number of Mini Clamp meters that have high resolution and are ideal for measuring low AC & DC current. These meters are smaller in size than traditional clamp meters and will easily fit into tight spaces. You can view the complete specifications of our mini clamp meters online. If you need more assistance, please contact our Tech Support for further assistance.

Extech and FLIR have a number of clamp meters that have Inrush measurement capabilities. You can view the complete specifications of our Clamp Meters online. If you need more assistance, please contact our Technical Support team for further information.

Controllers (Specialty Meters)

The physical size is different. The 46VFL is a 1/16 DIN panel size and the 96VFL is a 1/6 DIN panel size. The 48VFL has a single active output and the 96VFL has 2 active outputs, one main and the other secondary which operates opposite to the main output.

The last 2 characters of the model number indicate the output type. The “11” series has a reed relay output and the “13” series has a 4 to 20mA output.

Force Gauge (Force/Torque/Vibration)

Force gauges (475044 and 475040) – we have a kit of replacement parts (p/n 479097) which consists of 2 each of hook, flat, cone, and chisel head adapters.

Hygro Thermometers

An error message will appear on the display if the meter fails an internal diagnostic test.

E2 Calibration error. Recalibration is necessary.
E5 Relative Humidity sensor failure. Repair/replacement is necessary.

Extech has a few meters that can perform GPP (Grains per pound) measurements. Hygro thermometers like the RH520A and RH490 and also some of our Psychrometer moisture meters, like the MO290, MO295 and MO297.

IR Thermometers

Measurements should normally be made as close as possible based on the Distance to spot ratio of the meter. The meter can make measurements from a distance, however the accuracy can be affected by multiple factors like light reflections on the target, air temperature and humidity, also the size of the target and how shiny the target is. If you have questions, please contact our Tech Support team.

IR Thermometers measure the surface temperature of an object. The thermometer's optics sense emitted, reflected, and transmitted energy. The thermometer's electronics translate the information into a temperature reading which is then displayed on the LCD. The amount of IR energy emitted by an object is proportional to an object's temperature and its ability to emit energy. This ability is known as emissivity and is based upon the material of the object and its surface finish. Emissivity values range from 0.1 for a very reflective object to 1.00 for a flat black finish. If an object's surface is highly reflective, apply masking tape or flat black paint to the surface before measuring. Allow time for the paint or tape to adjust to the temperature of the surface it is covering.

An IR thermometer with adjustable emissivity can be used to compensate for the emissivity of different materials. Most organic materials and painted or oxidized surfaces have an emissivity factor of 0.95.

Material under test Emissivity Material under test Emissivity
Asphalt 0.90 to 0.98 Cloth (black) 0.98
Concrete 0.94 Skin (human) 0.98
Cement 0.96 Leather 0.75 to 0.80
Sand 0.90 Charcoal (powder) 0.96
Soil 0.92 to 0.96 Lacquer 0.80 to 0.95
Water 0.92 to 0.96 Lacquer (matt) 0.97
Ice 0.96 to 0.98 Rubber (black) 0.94
Snow 0.83 Plastic 0.85 to 0.95
Glass 0.90 to 0.95 Timber 0.90
Ceramic 0.90 to 0.94 Paper 0.70 to 0.94
Marble 0.94 Chromium Oxides 0.81
Plaster 0.80 to 0.90 Copper Oxides 0.78
Mortar 0.89 to 0.91 Iron Oxides 0.78 to 0.82
Brick 0.93 to 0.96 Textiles 0.90

Light Meters

The Extech EasyView EA30 is the only model that can measure light pulses/flashes or strobes. It has a peak hold feature that can capture short light pulses as fast as 100µS (100 microseconds).

Extech has Light Meters that can measure as high as 99,990Fc/999,900Lux with resolutions of 0.001Fc & 0.01 Lux. You can view the complete specifications of our light meters online. If you need more assistance, please contact our Tech Support for further assistance.

Extech has various light meters that are designed to measure the intensity of visible light, white LEDs, white and color (red, yellow, green, blue, purple) LEDs, and UV (sunlight).

The operation manual for your light meter will provide you with the basic information on how to make light measurements with your meter. Further light measuring procedures are outlined in local, state & federal lighting standards & compliance's that are applicable to specific applications.

Megohmmeter/Milliohm Meters

Extech does not sell longer leads for our Megohmmeters & Milliohm Meters.

The meters are calibrated with the standard length leads. If you application requires lead modification always make the leads from a second set of leads and retain the standard leads for calibration or meter performance verification.

Moisture Meters

It is meter dependent. Pin meters will read in % wood moisture and Pinless meters measure moisture in a relative scale. Check the data sheet for the meter of interest.

Extech does not have a moisture meter that will make accurate measurements in brick and concrete. Accurately measuring moisture in concrete (ASTM 2170) requires humidity plugs to be placed into the concrete surface.

Insertion into the wood should be to at least a 0.08" (2mm) depth for the highest accuracy. If this is not possible, carefully insert the test pins as far as possible without undue force.


Your Extech DMM has protective rubber holster that the meter fits into. The holster must first be removed from the meter in order to replace the battery. The battery compartment can then be accessed to change the battery.

Technical Support has a list of fuses used in our multimeters. We can provide the specifications for most fuses. Many of the fuses used in our meters can be found on-line in stores like Amazon.

Power Meters

The operations manual for each meter will instruct you on how to connect and setup your meter to measure 3 phase power measurements. The manual will also provide you with diagrams for these connections. Manuals for our power meters are available online. If you do not understand the information contained in the manual please contact our Tech Support for further assistance.


Extech has some power analyzers that can measure Transients and Harmonics. See our PQ3470 and Pq3350 meters. Be sure to check the data sheets of the meters of interest to be sure that they can measure all of the parameters that you require.

Extech does not have a power analyzer that can make measurements from a VFD. Our parent company (FLIR) does have Power Clamp meters that can make these measurements. See the FLIR T&M web page to review these meters.

Pressure Meters

The fitting is PS 1/4 inch 19 threads, not 1/4 inch NPT.


The operations manual for your meter will contain complete product details as well as specifications and resolution specs for each range. If you do not understand these specs please contact our Tech Support for further assistance.

Sound Level Meters

The meter would be a Type 2 meter. Type 2 meters meet the ANSI and IEC standards which conform to OSHA Guidelines.

The bandwidth measured is 31.5Hz to 8KHz.

It depends on what the meter is being used for. Check with the regulatory body you are testing to. OSHA compliance testing absolutely calls for a meter to be checked for calibration before and after every use.

"A" weighting processes sound in a manner similar to that of the human ear. "C" weighting does not apply any filtering to the measures sound. A weighting is typically used in OSHA compliance and town ordinance applications.


For measuring objects that are hard to reach or dangerous, the best solution would be a laser, photo, or strobe tachometer. Contact tachometers are used by pressing and holding the tip of the meter against a rotating object. Contact tachometers measure in linear feet or meters per minute.

The tachometers that use reflected light require the tape. These would include all of the Photo and Laser tachometers. The Strobe units do not require reflective tape.


Extech has a number of temperature probers including bead wire thermocouples and stick probes to be used in liquids. See our list of available probes on our Thermometer Accessories web page.

Extech has some temperature probes that can measure high temperatures. We also have distributors who carry compatible probes for any application. Contact our Technical support team for more information.

Optional AC adaptors are available for some of our thermometers. You can view the data sheet for a particular model online. If you need more assistance, please contact our Tech Support for further assistance.

Dashes are an indication that the temperature probe is not recognized by the meter. This could be due to a broken probe, or a bad connection between the probe and the meter. Check the orientation of the spade lug probe connector to ensure that it is inserted completely and correctly. Also try a new probe. If the problem is not solved, please contact our Repair department to repair the meter.