Monitor Submetering Options
A measurement for a quantity of electric energy, at any
point in time, is called a "watt". Example,
100W bulb, 1500W hairdryer or electric heater, etc. To
simplify the numbers, 1000 watts equals a "kilowatt"
or simply kW. This energy measured over time is
called a "Kilowatt-Hour" or "kWh".
One kWh means the usage of 1 kW for one hour or sixty
The traditional utility glass meter monitors and records
kWh increments on a digit counter or dial counter. The
electric energy usage is simply a continuous accumulation
of kWh counts.
In addition to recording kWh, most electric energy meters
also have a built-in method of determining short-term
interval or real time kW. Glass utility meter has a rotating
disk, ET-SP has a pulsing LED and direct kW readout
on a PC upload capability.
- Utility meter disk - by counting the black mark rotations
over a short interval time (60 seconds) a simple formula
can easily calculate or represent the average kW energy
over the selected time.
- Example - 4 REV, 72 seconds = 1.44 kW or 1,440 watts
- Note: The "7.2" number is the Kh designator
or value of the meter itself. In normal residential
meter this is 7.2 and the Electro Industries' electronic
meter it is also 7.2. In other metering arrangements
this can be a combination of the CT ratio and the
actual meter Kh. In the case Electro Industries' ET-SP
series the CT ratio is not used to determine Kh, for
simplicity all units are pre-calibrated with Kh =
- ET-SP series - a pulse from the yellow LED is identical
to a black mark rotation from the glass meter. Apply
the identical formula above, 1 LED pulse is 1 REV.
- ET-SP series - loading Electro Industries' proprietary
software (Windows based, ET-SOFT-SP) and a special cable
from any PC 9 pin com port, will allow any PC to display
the real time kW value and is retrieved with a simple
ALT-D keyboard function.
- Off-peak rate
- Industrial equipment energy monitor
- Apartment sub-metering
- Marine boat dock plug-in
- Mobile home/RV park
- Rental parking stall plug-in
- Electric heat rate
- Dual fuel rate
- Load survey monitoring
- Remote kWh register
- Automatic meter reading input
Electro Industries’ Electronic Sub-Meter
Designed for low cost and simplified installation.
The metered load power wires are simply strung through
the “doughnut” device commonly called CT. This can
be one load or several. Each power source wire is
run through the CT. This becomes the current or
“amp” component for the kWh energy calculation.
The meter module is connected to a convenient 120 or
240 voltage source. The setup parameters determine
whether this source should represent itself, 240, 208,
or 277/480. This becomes the voltage component for
the energy kWh calculation.
The meter module has precise digital measurement capability
and software to correctly monitor and record the electric
energy. In addition to storing the energy kWh values
within itself, there are hardware ports and software conversion
options for a variety of outputs.
A Palm OS™ or standard PC computer is used to:
- Download various setup parameters and/or offset for
- Display real-time Amps, Volts and KW. This means the
connected computer (Windows) has direct access to real-time
- Single or 3-phase
- Three CT sizes and accuracy
- 80, 160, 360-amp range
- 120 or 240 reference voltage monitor
- Internal LEDs
- Non-volatile internal kWh storage
- KYZ output
- kWh pulse output
- Palm or PC computer connection (Special cable required)
- Palm or PC download parameters
- Palm or PC amps and kW real time readout
- Field calibration, Palm readout compared to known
standard meter value
- Load down calibration offsets
Remote kWh Devices
Any basic pulse input counter can record and display
the accumulative kWh value. Options:
- Basic mechanical counter, 12-volt DC pulse
- Weather-tight and meter sealable counter
- Electronic pulse counter
Electro Industries’ Sub-Meter – Emulates
Basic Utility Type Meter
- Internal calculation base is 7.2 Kh (includes CT)
- LED pulse, same as utility meter disk black mark
- KYZ pulse is at 7.2 Kh
- Indoor, three individual pieces
- Outdoor/weather-tight, meter module is in drip-proof
enclosure (Weather-tight remote register can be mounted
next to utility meter enclosure)
- Installed within Electro Industries’ heating equipment
(Example – Electro-Mate, Dual Energy Furnace, Electro-Boiler,
- Two CT’s can be used, second is remote for water
heater or other off-peak load
A. Some configuration parameters relate
to specific hardware component sizes, CT type, method
of stringing CT, reference voltage, etc. These are factory
assembly controlled and are represented by specific model
number within the ET-SP product family.
- Single phase
- 240 reference voltage
- Maximum current - 80 or 160 nominal
- Kh = 7.2
- CT strung - both leg across or one leg only
B. Using PC software (and special cable) user can easily
download other variables.
- Nominal power factor
- Preset internal kWh register
- Single point voltage calibration offset
- Single point current calibration offset
PC 9 pin com port (typically COM1 or as setup under the
Communications menu) is connected to this unit with Electro
Industries' manufactured and furnished special cable.
This cable typically has the 9-pin connector on one end,
a "barrel" containing circuitry approximately
halfway along the cable, a flat cable going to a flat
6-pin connector. If ordering separately, request ET-RS232-WF.
On this unit's circuit board locate the small pin plug
(J1) soldered to the board. This is a 6-pin header with
the second from the top pin cut off (5 pins sticking up
Observing the special cable flat connector end, you will
notice the second hole from one end is plugged. This will
be the keying pin when plugging into this unit's circuit
It is permissible to plug in with this unit's power on;
however, realize there is power on the board and around
the transformer it is 240, line voltage.
This unit must be powered up (green light on) to activate
or read data from the PC.
Initiate PC using normal Windows process and procedures.
This software also has a HELP file. The primary field
usage of this software will be the first screen or ALT-D.
Repeated samples (or data reads) can be accomplished by
pressing the space bar.
For field calibration, use ALT-R.
There are other calibration routines within this software,
the user should not go there, unless directed by Electro
Industries' factory representative.
Real Time kW Monitor (also Checking Multi-Loads)
The PC first screen (or ALT-D) shows a calculated kW
each time the space bar is pressed. This is for observation
purposes only, but allows the user to verify kW at any
Multi-loads - this kW value can be used to quickly
verify proper CT stringing when monitoring multi-loads.
- Using source circuit breakers, only turn on the first
load (the one which provides 240 to this unit) and have
the other breakers off.
- Verify kW value approximately represents this load.
- Turn on the next circuit breaker, recheck kW displayed
and verify it has increased by the value of the load.
- Turn on next consecutive breakers and verify the kW
value continues to increase in approximate correct value.
- If at any time, when adding loads, the kW value (pressing
space bar) decreases, the wires going through the CT
for that load are incorrectly strung.
Field or User Calibration
Comment: If the yellow LED is not on solid, this unit
has been factory calibrated with certified and traceable
volt meter and current meter. This calibration is accomplished
at approximately 10% and 90% current end points and at
105 and 130 voltage points. Also the approximate midpoint
is rechecked and current and voltage offset are downloaded
to bring these midpoints to the exact current and voltage
represented by the factory calibrated instruments. Realizing
this, the following should be used as an overall verification
of the correct operation and accuracy of this unit, but
the user must discern the accuracy of his voltage and
amp meter before downloading any offsets or before attempting
to recalibrate this unit. In simpler terms, clamp-on amp
meter is not a very accurate device. However, it can be
used to make sure things are within "range".
- Select a load value or monitoring point which represents
the majority of the energy recording. Use handheld current
device to read the current to the load(s). If it is
multi-loads, all currents must be represented by the
field connected device.
- Attach volt meter to the same point represented by
the black and red wire going to this device.
- Using PC software, observe first screen, and acquire
a representative number of samples by repeatedly pressing
the space bar. Note the current and voltage values on
the screen and compare to the attached handheld instruments.
- If after careful observation user determines an adjustment
should be made, subtract (plus or minus) the values.
Note this difference (plus or minus) and proceed to
PC screen entry.
- Enter the plus or minus offset for either current
and volts. Permanently record this offset by selecting
the Communications menu and WRITE.
- If desirable (also suggested) go back to ALT-D and
repeat steps 3-5 above.
Warning: Suggest entering offset values of less
than ±2A. If it appears you need to enter an offset
greater than ±1, caution, there may be something
wrong with the setup, with the field instruments, calibration
AMR (Meter Reading Devices) Application
This unit contains an internal pulse initiator with an
open collector/emitter isolator interface at each "black
mark" point output is a 200 ms pulse. Typically the
external KYZ input meter terminal or AMR device is connected
to J2-1 and J2-2. Note: J2-1 (or red/blk wire) must be
DC positive. The AMR device is setup for 2-wire, KZ, and
Kh = 7.2. For convenience order accessory cable ET-KZ-SP
with easy plug-in connector and 4-foot wires.