What will the Key system do for me ?
One obvious advantage of telemetry is eliminating the need for driving across town to check on, or change, the status of equipment operating at remote locations.Telemetry also allows the utility to discover alarm conditions before they become critical events. You can monitor alarm conditions occurring at remote sites in "real time."
Another advantage of telemetry is in preventive maintenance. By utilizing the reports provided by Master Computer Software, the utility can diagnose problems long before they become failures. These reports allow the user to compare run times of equipment from day to day. These run times normally are very constant, so a variation in run times can indicate a problem.
Another valuable use of radio telemetry is being able to relay system status across town to initiate automatic control functions. The system can transmit status such as "pump run," "tank level," or "water pressure" from one remote location to another to activate control functions such as turning on chlorine injectors, or turning off well field pumps.
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What does Key recommend for the Master Computer ?
The Master Computer is usually a standard Personal Computer (PC) with monitor, printer etc. permitting the operator to monitor and control the field data.The PC serial port is connected to a suitable modem for communication with the Remote Terminals. The PC may drive a local printer, alarms, charts or other devices through one or more of its output ports. All cables and
drawings are supplied with your system, assuring a seamless installation using non-technical
personnel. |
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Tell me about the Master Program.
The PC programming varies widely from simple no cost canned programs for monitoring, to complex software written to your specifications. These programs are written in MicroSoft Visual Basic. Call me, Brent Hazelwood, I will be glad to discuss your application with no obligation to purchase. |
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What is a Remote Terminal Unit ?
A Remote Terminal (RTU), usually located at a field location, converts the analog values,discrete,
and counter signals into a serial digital format.This permits all signals to be transmitted on a
single telephone pair or radio circuit.The RTU consist of a small computer, modem, signal
converters and a non-interruptible power supply.The RTU options include modem type, clock-calendar, additional Input-Output (I/O) signals and housing. |
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How does the Master communicate with the Remote Terminals ?
You may select one or mix of several means of communication. They are leased telephone lines, standard dial up telephone lines, cellular telephones, or UHF-VHF radio. Your selection will be based primarily on cost and circuit availability.
Leased Lines are reliable and require less initial investment in equipment. If data is
required in real time, perhaps every few minutes, the leased line is often specified.There
is a monthly fee for the line use, charged in mile increments.The Bell compatible 202
Modem is the industry standard for these circuits. Key manufactures a full line of 202
modems for both the Remote Terminals and Master Station.
Dial Up Lines are well suited when the data needs to be accessed less often.Again the
investment in equipment is low and the telephone rates are about $50.00 per month for each
site, plus long distance charges.The modem used here is the CCITT standard, the same
unit that is supplied in virtually every personal computer.Key uses an off the shelf unit for
the Master site and has a built-in modem for the Remote Terminal.
Cellular Circuits function similar Dial Up Lines except special telephones and modems are
required at the Remote Terminal. The Key 300H Cellmate has all the required equipment
and will connect directly to the Datrax Remote Terminal.
VHF-UHF Radio requires the investment of a transmitter-receiver and antenna for each
site, however there no monthly fees.Distances are normally limited to line-of-site from antenna to antenna. If the cost is justified repeaters may be added.If you are eligible a system licensed by the FCC may be your best selection. Non-licensed frequencies are also available.Radio communication is often simple and straight forward, however it may become complex and require a system study.Contact me, Brent Hazelwood, for a free evaluation. |
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What does Analog Input or Output mean ?
The Analog Input Signal indicates the value of a function being measured.Some examples are pressures, liquid level, power etc.A device called a "Transducer" or "Transmitter" is used to convert the measured function into a current or voltage that varies in direct proportion to its input value. The industry standard is 4-20 Milliamperes (mA), however other values are often
used. A typical Transducer might output 4 mA for zero pressure and 20 mA for 500 lbs. The
Key Datrax Remote Terminal Units (RTU) fully support the value you specify.Analog output
signals are also usually 4-20 mA and they are used to remotely control devices that require
an incremental adjustment or a variable set-point. |
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Describe Discrete Input and Output.
Discrete or Digital input indicates the status of a single wire circuit. It is normally connected to
a switch, relay or other device with electrical contacts. These are used to indicate an Alarm,
On/Off, Open/Close, Stop/Run etc.Discrete Output is used to drive external relays, solenoids
etc.You may remotely control valve position, lights, Stop-Start engines or any other equipment
that can be controlled by relay contacts. |
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What is the function of a counter input ?
The counter measures the frequency or totalized value of a string of pulses or contact closures. This might be useful to measure RPM, turbine meters, part count etc. |
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What is RS-232 ?
RS-232 or Serial Communication is an IEEE industry standard for bi-directional communication over short distances. The Datrax uses this port to communicate with modems, printers, laptop and personal computers.Often only three lines are required (Send, Receive & Ground). |
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