Definition : Measuring instruments designed to measure the frequency of electric signals in one or more different ranges from a few hertz to several gigahertz. These instruments usually consist of an electronic unit including controls, a display, and attached cables and probes appropriate to perform the measurement. The counters may also include computerized capabilities to process the signals and outputs that permit recording, printing, and/or further processing of the results. Frequency counters are also used to measure time and/or the period of the signals as an inverse relationship to frequency.
Davis Instruments has been one of the world's leading sources of test, measurement, control, and calibration instruments since 1912. You depend on the equipment you order—and the technical expertise that backs it up. Since 1912, Davis Instruments has built a history of supplying customers with innovative test, measurement, control and calibration technologies. But what really gets customers talking is our "Customer First" responsiveness, which is woven into every transaction. From answering your most challenging technical questions to providing alternate configurations, you can count on Davis Instruments' application specialists to help you get the job done.
Extech Instruments is based in Waltham, Massachusetts USA, just west of Boston. Recognized for the breadth and depth of its Test & Measurement offering and strong distribution network, Extech was acquired by FLIR Systems in November 2007. Extech Instruments' high-value, handheld test instruments and FLIR-branded infrared thermal imager are sold through a network of national catalog houses, regional stocking distributors, internet, and international master distributors.
There are 3 types of search. Please only use one option at a time.
1) Build a boolean search string.
Ensure that document matches include...
2) Search for a phrase:
3) Search on part of a word:
Information on how to use Search
There are 2 types of basic queries: Terms and Phrases.
A Term is a single word search.
A Phrase would wrap a string of words in quotes and find matches on the extact string.
Boolean Operators You can combine basic queries with Boolean operators to form a more complex query. Boolean operators define the relationships between Terms or Phrases. Our search supports the following Boolean operators: AND, "+", OR, NOT and "-". Please note that Boolean operators must be all uppercase.
AND example search: default AND document
This is the default operator. It will be used if there is no Boolean operator between two terms. For example:
default document is the same as default AND document. In this case both terms need to exist within a listing to find a match on that listing.The + character is synonymous with using AND.
OR example search: default OR document
In this case just one of the terms needs to exist within a listing to find a match on that listing.
NOT example search: default NOT "document type"
The NOT operator excludes documents that contain the term (or phrase) after NOT. So a listing match would have to include the word default but not the phrase "document type". The - character is synonymous with using NOT.
Wildcard/Prefix queries You can perform "wildcard" or "prefix" queries using the '*' operator. Whereas all of the previous search found exact matches on the whole term or phrase, a wildcard search will find partial matches.
example search: ehr*
This query will match all documents containing words beginning with the prefix 'ehr' like the word Ehrlichia.
