Power Meter Documentation
Product Descriptions
The EZ Meter line of power 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 power 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 power 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 fromR. 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.
Power Line Carrier
These meters communicate over the power line back to a computer. They use a technology similar to the old X-10 protocol for home automation. The advantage is cheaper installation costs. The disadvantage is that other things can interfere with the communication signal. You need to order a RS-232 to Twisted Pair Interface (Model 4810) to connect to the computer and a Twisted Pair to Power Line Interface (Model 4820) to connect to the power line. A twisted pair of wires connects the two interfaces. Signal coupling capacitors need to be installed at the end of all lines and at major branches of the circuitry (such as at breaker panels).
Dedicated Twisted Pair
If installing a twisted pair of wires is not a problem, the dedicated twisted pair is the preferred way to go. There are none of the system configuration limitations of RS-485 and you are free to connect the meters together in a star with wires going off in different directions or a daisy-chain with wires looping from one meter to the next. The number of meters is unlimited and the distance is up to five miles.
Inputs, Outputs, Pulse Counting
The Plus IO meters all have three IO ports that can be used for inputs, outputs,or counting pulses from water, gas, or other electric meters. The EZ ReadIt software package controls the IO ports.
When an IO port is used as an input, it can tell if a switch is open or closed. This can be useful for detecting if someone is tampering with the meter. It can also be used to signal maintenance is required or to activate an alarm for fire or intrusion. The IO port can also be used to activate a relay to turn on lights or any other device, even to turn on the power at a pedestal in an Remark. The power meters are normally shipped with enough output power to light an LED. If you need more than that, specify the amount of power you need and the meter will be custom configured to supply that power. When used for pulse counting, the power meter detects every change of state of the switch and accumulates the total separately for each port. A cost effective meter reading system would use one PLUS IO meter and three of the stand alone meters with the pulse output option.
If tenant tampering with the power meter is a real worry, two IO ports can be connected to tamper switches. The one connected as an input tells the condition of the switch at any time and the one connected as a pulse counter tells how many times the tamper switch has been activated.
Local Display
Each power 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 power 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 USB 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
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 power 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 to see the state's submetering regulations, last updated in 1995. Look for Article 2.2 or search for 'watt-hour meter'. The latest draft that we know of has not been implemented yet. It is important for marina operators that it be implemented because the old regs specify a 30" mounting height. 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.
Printable Brochures
Use the Adobe Acrobat print button to print the first page, then feed the paper through again and print the second page on the back. It will create a tri-fold brochure that gives a brief description of each meter. Prices shown in brochures are for a typical meter. See the Online Store for pricing with the options you need.
Installation Instructions
Similar to the brochures, the Installation Instructions makes a four-panel brochure when printed on one sheet of legal size paper.
Specifications
Specifications are printed on the back of 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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