Bosworth Instrument
bosworth Airflow Meters
bosworth Boroscopes
bosworth Calibrators
bosworth Clamp-On Meters
bosworth Electrical Testers
bosworth Fiber Optic Meters
bosworth Force/Torque/Vibration
bosworth Gas Detectors
bosworth Humidity Meters
bosworth HVAC
bosworth Label Printers
bosworth Light Meters
bosworth Material Testing
bosworth Moisture Meters
bosworth Multimeters
bosworth Multimeter Accessories
bosworth Power Supplies/Analyzers
bosworth Pressure Meters
bosworth Psychrometers
bosworth Refractometers
bosworth Sound Meters
bosworth Stopwatches/Timers/Clocks
bosworth Tachometers
bosworth Thermal Imaging
bosworth Thermometers
bosworth Water Quality
bosworth Water Quality Accessories

General Questions

 My meter has problems communicating with the software installed on my computer (applicable models w/ RS-232 interface)?

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

* * *

Is my meter calibrated out of the box? How often should it be calibrated? Does it come with a calibration certificate? How & where can I get my meter calibrated?

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 at (781) 890-7440 X210 for a return authorization number and other return information.

* * *

Where can I obtain a User’s Guide for my meter?

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.

* * *

How often does my meter need to be calibrated?

Extech meters should be calibrated annually.

* * *

How can I get a calibration procedure for my meter?

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

* * *

Can you cross reference another manufacturer’s product to an Extech product?

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  You may also reach us by phone at (800)-804-6216.


Airflow Meters

How do I set up and calculate for measuring CFM’s (for applicable models)?

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.

CFM/CMM Area Measurement Formula

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


* * *

Does Extech have an Anemometer product that has a sensor that will work with temperature applications above 175°F?

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.

* * *

My Vane/Hotwire probe is broken, can I simply replace it?

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

 I clamped around an AC Power Cord and I am not getting a measurement. Why?

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).

* * *

Do you carry clamp meters specifically made to measure low current?

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 call the Extech Tech Support Hotline at (781) 890-7440 X200 to speak with a tech support representative to discuss your specific application needs.

* * *

Do you have a clamp meter with a Peak Inrush Current feature?

Extech has a number of clamp meters that have a "Peak Hold" feature for capturing inrush currents and transients. You can view the complete specifications of our clamp meters online. If you need more assistance, please call the Extech Tech Support Hotline at (781) 890-7440 X200 to speak with a tech support representative to discuss your specific application needs.


Controllers (Specialty Meters)

 What is the difference between the 48VTR and the 96VTR controllers?

Physical size is the basic difference. The 96VTR is larger (1/8 DIN) while the 48VTR is 1/16 DIN.

* * *

The 96VTR also has two alarm relays. The 48VTR has one alarm relay. I purchased a controller. Is it the right configuration for my application?

The last two characters in the controller part number define the type of input and the type of output. For example, 48VTR11 is configured for a thermocouple input and a relay output. The controller data sheet explains the various combinations available.


Fiber Optic Meters


How do I display the loss in my fiber link on my meter?

The FO, MO and PM optical power meters are all capable of displaying the optical loss in a link. Optical loss measurements are always given in dB. A power meter, a light source, and at least one patch cord are required to measure the optical loss in a fiber link.

Optical loss measurement is a two step process: setting a reference, and testing the fiber link.

To set the reference in the meter, otherwise known as "zeroing", attach the light source to the meter via the patch cord. Make sure that the units are powered on, and are set to the same wavelength (e.g. 850nm). You may now set the reference in the meter. Each meter has a different way of setting zero, so consult the manual for instructions. Double check your zero point by setting the meter to dB mode. The number on the display should be approximately 0.00 dB.

Once you have set the zero point in the meter, you are now ready to test your fiber link.

PLEASE NOTE: do not disturb the connection to the light source. If you disconnect the patch cord from the light source between the time you zeroed the meter and tested the link, then your reference, or zero, point will be invalid. If you are testing at two wavelengths, then either a duplex patch cord, or two patch cords, are recommended -- one for each light source port on the light source.

Disconnect the patch cord from the meter, and take the meter to one end of the link, and the light source to the other end. Connect the meter and the light source to the fiber being tested. Set the meter to display units in dB. The resultant number will show the amount of loss in the link as a negative number.

Example: We are testing a fiber link at 850nm. When we connect our 850nm light source to the meter, the dBm reading is -20.10. We toggle to dB mode and see that the meter shows a reading of 0.00 dB. When we disconnect the patch cord from the meter, take the units to opposite ends of the fiber link, and connect them to the fiber under test, our meter shows -1.24 dB. What this means is that the fiber link is losing 1.24 dB of optical power due to the total loss of the passive components of the fiber link (fiber loss, connector loss, and splice loss).

Optical loss can be used for PASS/FAIL readings as well. The actual optical loss number on the meter is compared with the theoretical PASS/FAIL threshold calculated on your link budget calculation sheet. A link will PASS when the number on the meter is between zero and the PASS/FAIL number. Likewise, a link will FAIL when the number is lower than the PASS/FAIL number.


* * *

Do your meters measure length?

Only the FO620 includes an integrated length tester. It cannot locate distance to a fault as it is not an OTDR.

* * *

Can I get a NIST certificate with my power meter and light sources?

All power meters and light sources come with the NIST certificate.


Force Gauge(Force/Torque/Vibration)


Do you have replacement parts for the force gauge?

The replacement hook p/n is 475001. The p/n for the replacement tips is 479097. Contact customer service or your local distributor.


Hygro Thermometers


I have a Model 445580. What does an E2 or an E5 error message mean?

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.


* * *

Do you have a meter that does GPP? (Grains per Pound)

Extech does not have a Hygro Thermometer that can measure GPP. However, please continue to check our website for information on new products.


IR Thermometers


Will my IR meter measure accurately 10 feet from the target?

Measurements should normally be made as close as possible to the device under test. The meter can measure from moderate distances but the measurement may be affected by external sources of light. Steam, dust, smoke, etc. can also obscure measurements. In addition, the spot size may be so large that it encompasses surface areas not intended to be measured.

* * *

My meter seems to provide readings that are too high or to low when measuring metal surfaces. Why?

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.

* * *

Why do I need a IR meter with adjustable emissivity?

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.

Emissivity Factors for Common Materials

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


Do you have a light meter that measure light pulses/flashes or strobes?

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).

* * *

Do you have a light meter that measures very high light levels?

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 call the Extech Tech Support Hotline at (781) 890-7440 X200 to speak with a tech support representative to discuss your specific application needs.

* * *

Do you have a meter that can measure colored light and light forms other than visible light (LED’s/Blacklight/UV)?

All Extech light meters are designed to measure the intensity of visible light only (400 to 760µm). Extech does not have a product that can measure other forms of light (LED’s/Blacklight/UV etc.)

* * *

What is the correct procedure to make measurements with my light meter?

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


Do you sell longer leads for my meter?

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

* * *

Can I lengthen or modify the leads that I have?

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


Does my moisture meter read moisture content or does it give me a relative reading?

It is meter dependent. Some of our moisture meters directly read % wood moisture and others provide a relative scale. Check the data sheet for the meter of interest.

* * *

Do you have moisture meters that will work on brick, concrete & other construction materials?

Yes, the Extech model MO400 can be used to measure moisture in brick, concrete & other construction materials.

* * *

For making wood measurements with the pin style moisture meters – how far do the pins on my meter need to be inserted for an accurate measurement?

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.

* * *

Can a 407777 moisture meter be used to measure moisture content of drywall?

The meter can be used to make comparative or relative measurements on drywall. Download the users manual from our website for detailed instruction on this operation.

* * *

Do you sell replacement pins for the 407777 moisture meter?

The replacement pins are P/N 407779. Contact customer service or your local distributor.




How do I change the battery – I’ve read the manual and do not see the battery compartment?

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.

MultiMeter Battery Replacement Procedure


* * *

How do I get spare fuses for my Multimeter?

Spare fuses can usually be purchased at Radio Shack or other electronic stores.


Power Meters


Do you have a Power Analyzer that can measure higher than 20 amps?

Extech model 382068, 382090 & 382095 Power clamp meters can measure higher than 20 amps. Models 380801 & 380803 can only measure up to 20 amps.

* * *

Regarding models 382090/382095 - How do I set my meter up to measure specific 3 phase power applications?

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 call our Tech Support Hotline at (781) 890-7440 x200 for further assistance.


Pressure Meters


What are the thread sizes for the pressure transducers for model 407495?

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

* * *

Where can I find the accuracies and resolutions for the ranges on my pressure meter?

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 out Tech Support Hotline at (781) 890-7440 x200 for further assistance.

* * *

What are the specs on the connectors and tubing that come with the 407910 meter?

The connector can withstand pressure up to a maximum of 10.5kg/cm2. However, the meter can only withstand pressure up to 3kg/cm2 max. The tubing size is 6 x 4mm and can be used for air or non-corrosive/non-ionized gas.


Sound Level Meters


What type of sound level meter do I need to comply with OSHA regulations?

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

* * *

What is the frequency bandwidth of your Sound Level Meters?

The bandwidth measured is 31.5Hz to 8KHz.

* * *

Do I need to purchase a microphone calibrator?

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.

* * *

What is the difference between A and C Weighting.

"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.




Do you sell the adaptor sleeve for the contact tachometer?

The replacement sleeve is P/N: 461889. Contact customer (800) 804-6216.

* * *

What tachometer will best fulfill my application – Photo, Contact, Lasser?

For measuring objects that are hard to reach or dangerous, the solution is the photo or laser tachometer. The contact tachometers have to be used by pressing and holding against the rotating object. Only contact tachometers can measure linear feet.

* * *

Do I need to use the reflective tape?

Yes. The tachometer works by bouncing light off of the tape and needs this highly reflective surface for optimum results.




Do you have a temperature sensor to fulfill a specific need?

Extech has a complete line of temperature probes.
For more information visit Thermometer Accessories section.

* * *

Do you have temperature sensors that are rated to read very high temperatures?

Extech has a complete line of temperature probes.
For more information visit Thermometer Accessories section.

* * *

Do you have an AC adaptor for my unit?

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 call the Extech Tech Support Hotline at (781) 890-7440 x200 to speak with a tech support representative to discuss your specific needs.

* * *

The display on my thermometer says OL all of the time – How do I correct this?

An OL could indicate that the thermocouple is defective, plugged in backwards, or not seated completely. Check the orientation of the connector and reseat the thermocouple to make sure that it’s plugged in completely. Try replacing the thermocouple with a “known good” thermocouple. If the problem persists, the thermometer should be sent in for repair.


Bosworth Instrument 1995 E. 55th St.  Cleveland, OH 44103  |  800-804-6216  |