KWH Meter Documentation
Product Descriptions
The EZ Meter line of KWH meters are intended for submetering applications. While they meet or exceed the accuracy standards of most utility company meters, they do not fit in the meter socket used by the public utilities. The meters consist of three components: (1) an electronics module, (2) one, two, or three current transformers (CTs) for sensing the current, and (3) a display that shows the accumulated kilowatt hours. The CTs are usually installed in a breaker panel or disconnect box. The electronics module is usually mounted in a NEMA approved enclosure near the CTs. The display is usually mounted on the outside of the electronics enclosure. Our stainless steel mounting plates make that easy to accomplish.
While most KWH meters are installed with all the components near each other, there is no requirement that they be installed that way. You can easily extend the wires for either the CTs or the display counters 100 feet or more. If you extend the display wires, we recommend you purchase a 6volt display so the counter will not suffer from voltage loss from the extended wires.
Automatic Meter Reading Systems
Davidge Controls makes KWH meters in stand-alone versions and several versions with different Automatic Meter Reading (AMR) capabilities. You may choose any of these communication technologies: RS-485, RS-232, power line carrier(communication over the power lines) and a proprietary twisted pair using the power line signal on a dedicated twisted pair. Systems can be configured with telephone modems, TCP/IP interfaces for internet or LAN connections, radio link or directly connected to a computer.
RS-485
The RS-485 communication protocol uses two twisted wires to loop from one meter to the next. Up to 128 meters can be connected in one system. By using a repeater, additional meters can be connected. This protocol is widely used for industrial control applications and requires a special card in your computer or an adapter. Adapters can be purchased from R. E. Smith Co.
RS-232
Until recently, all Windows computers came with one or more serial ports. If your computer has one, you can connect it directly to the meter with a three wire cable. The big advantage is that additional adapters are not required. Up to 6 meters can be linked together.
Local Display
Each KWH meter, whether an AMR meter or not, can drive an electro-mechanical counter. The counters look like the odometers in cars a few years ago. The standard counter is intended for indoor use and is not sealed. Sealed counters are also available for use in marinas, RV parks and other outdoor locations. Counters between 6 and 12 volts may be used.
Telephone Modems, LAN Adapters, Radios
You can install any one of a number of long range communication devices between your computer and the KWH meters to be read. The device you install should have an RS-232 port or RS-485 port to connect to the meters. If you use a telephone modem, you will need a dedicated phone line because the meters only answer when they are called. The modem must be able to communicate at 1200 baud for the Power Line Carrier and Dedicated Twisted Pair systems or 9600 baud for the RS-232 and RS-485 systems. Useful links:
R. E.Smith for US to RS-232 adapters and all types of RS-485 adapters TechOnWeb for telephone modems. Order the MultiTech MT3334ZDX modem because you can set it to have high speed communication between the modems and 1200 baud to talk to the power line modems. Newport Electronics for their iServer MicroServer - TCP/IP to RS-232 interface ALX Technology for all types of radios
Safety Certifications
Meters for electrical systems that are 120 volts to neutral have been tested by CSA to UL Standard 61010-1 and are approved for use in the United States and Canada. None of the other KWH meters have been tested. Certificate of Compliance
Accuracy Certifications
We guarantee that all meters meet or exceed the accuracy standards of ANSI C12.1 (2001), the national standard for all type off power meters. The standard requires that the meters be accurate within 1% across there entire operating range. The range is a factor of 100 meaning that a 100 amp meter will be accurate from 1 amp to 100 amps, a 200 amp meter is accurate from 2 amps to 200 and so on.
Special California Regulations
The State of California, Division of Measurement Standards has certified the accuracy of the 100 and 200 amp KWH meters for 120 volt to neutral, 240 volts line to line electrical systems. These meters are the only ones that can used in California for revenue billing. Each meter must be tested by the local Weights and Measures office before being installed. Click here for a copy of the acceptance certificate. Click here for the state's submetering regulations, then search for 'watthour' or find Article 2.2. Briefly, the regulations say that all meters use for revenue purposes must be type approved by the state and inspected and placed into service by the County Sealer from the local Weights and Measures office. It is a misdemeanor not to follow these regulations. Each electric utility company can make their own rules as to who can resell their power. Most of the utilities in the state allow resale of power at marinas, RV and trailer parks, and in master metered residential buildings built before 1982. See the PUC opinion for details about buildings not originally built for residential uses. Because it is also a misdemeanor for us to sell a meter within the state knowing that it will be used illegally, we require all purchasers to complete this form and fax, email, or mail it to use before we will ship a meter within the state.
Installation Instructions
Specifications
Specifications are included in the data sheets for each of named meter systems.
Go to the Products page and click on the meter name to see the data sheet and specs.
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