tehama wireless AN-117 Encoded Meter User Guide
- June 5, 2024
- tehama wireless
Table of Contents
AN-117: Encoded Meter FAQ
AKA an Encoded meter Decoder guide
AN-117 Encoded Meter
We have encountered many questions over the years since we introduced our
encoder MDTs. There is some misunderstanding as to how these meters output
data and what products like the Tehama Encoder MDT are able to read from these
devices. This app note will cover this and other questions about encoded
meters.
Q: How do I wire the encoded meter to the MDT?
A: Please see our Application Note
Q: How do I wire the encoded meter to the MDT?
A: Please see our Application Note AN-102-E: Encoder MDT Wiring Guide on the
Resources page of the Tehama
Wireless website.on the Resources page of the Tehama Wireless website.
Q: What MDT model will work with which encoded meter?
A: All our MDT products whose part number suffix has an “E” in it will work
with both Sensus and Neptune meters. For example, MDT model numbers TW-140B-E,
TW-160B-EP, or TW-175B-EE. Almost universally, encoded meters from vendors
other then Neptune and some from GWF use the Sensus UI-1203 protocol and are
therefore compatible. Note that an early version of our MDT with model number
TW-140B-N will only work with Neptune meters.
Our recently introduced TW-160B-G and TW-170B-G AllRead Encoder MDTs are
designed to read GWF Unico2coder® MP water meters. This modified M-bus
interface transfers data about the meter’s unit of measure (gallons, cubic
feet, etc.), the counting factor, and the hot or cold designation of the
meter, in addition to the meter read and the serial number. The greatly
simplifies the MDT setup and guarantees an error-free
Q: How do I determine the Count Factor for an encoded meter?
A: The count factor might be printed on the meter’s register face (x10 or
x100). For many mechanical meters, it can be determined by the number of fixed
zeros to the right of the moving dials. For other registers there may be a
graphic that indicates only the top X digits that are available to the reading
device. Electronic meters with LCD displays can vary. Neptune for example can
only provide the upper six digits regardless of actual display width, so the
remaining digits should be treated like fixed zeros. On the other hand, a
Kamstrup meter will provide every digit shown on the display. It is best to
consult with the meter manufacturer.
Q: How do the encoded meter and the MDT communicate?
A: The interface between encoded meters and the MDT is based on a digital
handshake between the devices. The MDT is the reader and sends a query command
to the meter which will respond with the current reading as displayed on the
meter face along with the serial number of the meter. This data is in a
specific format (i.e. Sensus UI-1203 or Neptune formats) and the MDT will
interpret the response from either format and transmit the reading value. For
our GWF AllRead compatible MDTs, the information about the meter’s units of
measure, count factor, and Hot/Cold meter type is also read by the MDT.
Q: Will an Encoded meter turn on an MDT, like Pulse meters do?
A: Yes. An MDT that is in the Off state will still wake up once every 24 hours
to check if it is connected to a meter. If it receives a valid response from a
meter, the MDT will turn on and begin to transmit reads.
Q: What’s the resolution on a Neptune ProRead Mechanical meter?
A: On 1-inch and smaller meters there are six moving dials plus a fixed
(painted) 0 for the single gallon position, so the counting factor is 10. On
1.5 and 2-inch meters there are six moving dials and two fixed (painted) 0’s
for the 1 and 10-gallon positions, so the counting factor is 100.
However,
Neptune further reduces the effective count factor by only reporting a 0 or a
5 for the lowest moving dial. While the count factor is still 10 for this
meter (because of the one fixed zero), any reader such as our MDT will only
detect a change in reading every 50 gallons! For the larger meters with two
fixed zeros, the MDT can only detect a change every 500 gallons (and the count
factor is 100).
For the register shown above, the moving dials show 4138. Apply a 10X count
factor to the 4138 to get 41,380 gallons. However, the MDT will report 41350.
Why? Because of the of the 50-gallon resolution available to the MDT. Once the
register shows 41400, the MDT will report 41400.
This explains why in CIT-generated graphs of some Neptune meter data, you will
always see the value jump by 50 or 500 gallons (assuming you have applied the
proper count factor in the CIT).
Q: What’s the resolution on a Neptune ProCoder Mechanical meter?
A: On 1-inch and smaller meters there are six moving dials plus a fixed
(painted) 0 for the single gallon position, so the counting factor is 10. On
1.5 and 2-inch meters there are six moving dials and two fixed (painted) 0’s
for the 1 and 10-gallon positions, so the counting factor is 100.
The Neptune ProCoder register does not suffer from the limited resolution of
their ProRead register. The MDT will report the reads with a 10-gallon
resolution.
Q: What’s the resolution on a Sensus mechanical meter?
A: This depends on how the meter was manufactured or programmed at the
factory. Some Sensus meters have dials going down to the 1/100 of a unit
(gallon or cubit feet) but it may only supply some of the dials through the
electronic interface.
Q: What is the resolution on newer electronic encoded registers?
A: Newer solid state meters, easily identifiable with an LCD display and often
a solar panel, generally provide better resolutions compared to mechanical
meters. In the case of Neptune, their public protocol will only supply six
digits of data regardless of the number of digits displayed.
The picture here shows a 5/8” E-Coder register with nine digits
total, two digits of which are to the right of the decimal (1/100 of a gallon
resolution). But since only the upper six digits are available to the MDT, it
will report 466. Apply a 10X count factor to get 4,660 gallons when displayed
in the CIT or a daily report, even though the register shows 4,664.46 gallons.
Q: How do the encoded meters generate the read data?
A: For mechanical meters, there is either a magnetic or optical mechanism that
interprets the physical dial position. Here is a
YouTube video that demonstrates
the optical solution. The MDT (or touchpad reader) energizes the circuit in
the meter, which in turn sends the reads data to the reader. To simplify the
circuit, the meter manufacturers often don’t output the value of every
spinning dial, or sometimes they reduce the resolution of the rightmost
spinning dial. Note that a higher resolution sweep hand is never available to
an external reader as it is usually associated with the rightmost fixed
zero(s).
Q: How do I read the register on the meter face?
A: Please consult with the meter manufacturer on how to read their specific
meter.
In general, here are a couple of examples to help illustrate:
Contact us:
Tehama Wireless
2431 5th Street
Berkeley, CA 94710
415.495.7344
[email protected]
www.TehamaWireless.com
©2022 Tehama Wireless Design Group Rev.2207
AN-117 Encoder Decoder-1912
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