MicroDataLogger Frequently Asked Questions (FAQ)
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Contents
DATAMANAGER CONFIGURATION
MDL APPLICATIONS
MDL MODULES
SCALE FACTORS: SLOPE, OFFSET, UNITS, DECIMAL DIGITS, AND WARM-UP TIME
BATTERY
DataManager™ Configuration
- When running MDL-DataManager™ under Windows 95®, I get the error message "x-modem time out". What's wrong and what should I do?
- Usually re-booting your computer will eliminate the problem. If re-booting doesn't solve it, you may have another application in your Windows 95 Start Menu, which automatically loads each time your computer boots, that is conflicting with MDL-DataManager's communications through your computer's serial port. In Windows 95, depressing Crtl-Alt-Del displays a Close Program dialog box which shows all of the programs currently running. Highlight a program that you suspect may be causing a serial port conflict and choose the End Task button. If this eliminates the conflict, consider removing this program from your Windows 95 Start Menu.
MDL APPLICATIONS
- How often should I sample when taking temperature measurements?
- A general rule of thumb for analog signals including temperature is to choose a sample interval that is about twice as fast as you would expect the temperature to change 1 degree F. Sampling faster often results in a series of redundant readings. The thermistor temperature sensors supplied by AEC take about 30 seconds to respond to a change of 1°F. For most building energy lighting and HVAC monitoring applications, a sample interval of 1, 2, or 3 minutes is usually sufficient.
MDL MODULES
- When using AC current transformers, what terminals on the 333 mV AC module do the black and white wires connect to?
- The module wiring connections table is found in Appendix A on page 55 of the MDL-DataManager™ Version 2.0 Reference Guide. For the 333 mV AC module, use pin numbers 2 and 3. If you are making a single-phase measurement, it makes no difference whether you connect the white lead or black lead to either pin.
- What does the word "This Side Toward Source" printed on the current transformer mean?
- This means that when you connect the current transformer, you need to attach it so that the side with "This Side Toward Source" is facing in the direction the current is coming from. In other words, it should face towards the power source, or power plant. Note that this is very important when monitoring power with the Watt Node, or when monitoring more than one circuit with the same current transformer.
- Can I measure more than one circuit with a single current transformer?
- You can use a single current transformer to monitor multiple circuits in a panel. When doing so, the monitored wires must be going in the same direction, and they must be the same phase. For example, a three phase panel will have the below configuration. In this panel, you could monitor circuits 1,2, and 7 say, since they are all phase A, but could not add circuit 3, since it is a different phase (B).
| Circuit # | Phase | Circuit # |
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1
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A
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2
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3
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B
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4
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5
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C
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6
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7
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A
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8
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9
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B
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10
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- When I'm using the MicroDataLogger® with a 333 mV AC module connected to a current transformer (CT), I see accurate readings when viewing real time readings on the MicroDataLogger's LCD display. However, my logged data record shows readings that are much lower. Why?
- The 333 mV AC module's default warm up time is 2 seconds. When you open the Configuration Parameters dialog box for a 333 mV AC module, the default value, 20, will automatically be entered in the warm-up time field. Never reduce this value for the 333 mV module. When the MicroDataLogger's display is on, the 333 mV AC module is powered up and reads accurately. Similarly, the warm-up time of 2 seconds ensures that the 333 mV AC module is powered up before the MicroDataLogger® records it. It is only necessary to increase the warm-up time under rare and limited circumstances.
SCALE FACTORS: SLOPE, OFFSET, UNITS, DECIMAL DIGITS, AND WARM-UP TIME
Note: A
Scale Factor Calculator
as well as examples and indepth information are available on this website.
- What is warm up time and how should I set it?
- Warm-up time is measured in 10ths of a second, so that a value of 20 would mean the warm-up period lasts for 20/10ths, or 2 seconds. In general, you should accept the default value for warm-up time that displays in the Configuration Parameters Dialog Box. If you use a warm-up time of 0, no power will be supplied to that module before the MicroDataLogger® records a reading. The pulse and status modules do not require a warm-up time. When using transducers that require power, greater warm-up times may be required, depending on each transducer's power requirements. The 333 mV AC module's warm-up time should never be less than 20.
- How do I set the slope for a Pulse Counting Module connected to a WattNode?
- Note: An example of this calculation is presented in example #5 under Appendix B of the DataManager™ User's Guide.
On the back of the WattNode, there is a factor called "Watt-hours per pulse per CT rated Amp." Multiply this factor by the full scale rating (amps) of one of your connected CTs. Enter this product as your slope. Choose Watt-hr as your Unit. If you want your data in kilowatt-hours, divide the product by 1,000 and choose kWh as your unit.
- How do I measure kW with the WattNode?
- The WattNode is designed to measure watt-hours or kilowatt-hours. In order to measure kW, you will need to divide out the time interval (in hours) when calculating the slope for the WattNode. The time interval that you need to divide out will be the sample interval being used during the monitoring process.
For example, a three-phase, four-wire, 277/480V WattNode (WNA-3Y-480-P) is being used with three 200A CT's, and is collecting data at a sample rate of 5 minutes. In order to determine the slope for monitoring kW, we first determine the slope for monitoring kWh, which would be (0.05771) * (200) = 11.542 Watt-hours per pulse, or (11.542)/1000 = 0.011542 kWh/pulse. Now, since our sample interval is 5 minutes, we need to divide our slope by this time interval in units of hours. Thus, we divide 0.011542kWh by 5min/60min or 0.0833hours, and get 0.011542kWh/0.0833h = 0.1386kW. Our slope would be 0.1386 and our units would be kW.
BATTERY
Note: The MicroDataLogger® model 201 has been replaced by model 202 as of October, 1998. This new model features a single, longer-lasting more reliable battery than the model 201. Run-times are typically 30% longer than before, and a cared for battery should last for 5 years. If you currently own model 201 loggers, we strongly encourage you to contact AEC and upgrade these loggers to the model 202 (for $49 per logger).
The MicroDataLogger® is powered by an internal, rechargeable battery. The logger spends most of its time in a low-power sleep mode. Whenever it is time to take a measurement, the MicroDataLogger's real time clock wakes up the microprocessor to begin another sampling cycle. Each time the microprocessor wakes up, it checks the battery voltage and, if the voltage is too low (5.6 volts or less), it will stop logging and display a Low Battery Stopped alarm message. This protects the battery from being damaged by excessive discharge.
- How often should I charge the MicroDataLogger's battery?
- Before and after each deployment, charge the MicroDataLogger® overnight (8-12 hrs). When storing a MicroDataLogger® for an extended period, re-charge the battery every two months.
- How long will a MicroDataLogger® run on a fully charged battery?
- The operating time of the MicroDataLogger's battery depends primarily on the sample interval and the power requirements of the modules and sensors used. Under typical conditions, using low-power sensors, at a sample interval of 1 min., the MicroDataLogger® will operate for about 30 days. Low ambient temperatures will decrease battery capacity about 30%.
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