Technical Questions and Answers

The SmartReader Plus-2 logger’s external relative humidity channel can be used as a 0-2.5Vdc input. The signal from the EH-020A External Humidity probe is a 0-2.5Vdc signal. Insert the positive wire into the terminal labeled Rel. Humidity, and the negative wire into the Common terminal. Assign equation 7 to the channel to have the data scaled in units of DC voltage. If you have larger voltages, you can use an external voltage divider circuit to measure these voltages with the SRP-2 logger.

Please note that you cannot use the 8-bit SR-002 logger’s external RH channel for DC voltage measurements, as this logger does not have a voltage regulator on the RH channel.

Once you send a setup to a data logger, the logger will begin sampling immediately since you have it plugged into the IC-102 cable. You must close the communication port as the logger cannot be communicating with the computer in order for Fast Read to work. If real time is activated, the logger will stop recording.

In order to access a sample rate faster than once every 8 seconds, the SmartReader Plus loggers require the use of an external power supply. This power supply can be in the form of a Fast Sampling Battery Pack (BP-101), 120V power supply, or interface cable plugged into a communication port on a computer.

ACR has developed a battery pack with replaceable “AAA” batteries. The Fast Sampling Battery Pack has an 8 inch (20cm) cable attached, with a male stereo jack on the end. The stereo jack can then be plugged into the communication port on the data logger and this then powers the logger for recording at the faster sample rates. If FAST READ MODE is selected in the software in the setup, the logger will not begin recording unless the BP-101, PS-201, IC-101, or IC-102 is plugged in before the start delay has elapsed. If NORMAL MODE is selected, you do not need the external power supply, because you cannot sample faster than once every 8 seconds.Powering a SmartReader Plus with the Fast Sampling Battery Pack (BP-101), or 120Vac powered PS-201.

The only way the logger can be triggered to start is by using the delayed start. You should program a delayed start 8 seconds longer than desired because the accuracy of the delayed start clock is +/-8 seconds. The battery pack or power supply must be plugged into the logger before this delayed start elapses. If you remove the power source, the logger will stop recording. It cannot be restarted unless you send the setup configuration to it from TrendReader software, including a delayed start. The power source cannot be used as a trigger to start recording because of contact bounce when it is being plugged in. The BP-101 battery pack will power a logger for 7 days continuously before the batteries need replacement. The “dead battery” light will remain lit for 28 days after it first turns on and does not allow fast sampling when on.

Fast read mode is available for SmartReader Plus and OWL data loggers. Fast Read mode is supported by the SmartReader Plus and OWL loggers. This mode changes the logger’s onboard clock to allow faster sample rates (down to 0.04 sec on a SmartReader Plus and 0.2 sec on an OWL). To conserve power, the logger is forced into “Stop When Full” mode when Fast Read mode is selected. Any attempt to communicate with the logger will stop it recording. On SmartReader Plus loggers this mode will only record if a power source is connected to the communication port (either a computer port, battery pack or power supply providing sufficient current).

Cable Length Extensions for Probes and Communication Cables

This article describes the criteria for extending the cable length of ET-series Temperature Probes, EH-series RH & Temperature Probes, Thermocouple Wires and Communication Cables.

ET Series Temperature Probes

These Temperature probes use a thermistor sensor – the resistance varies with temperature. Since conductors have an inherent resistance, there is a limit to the length of cable that can be added to a thermistor probe without affecting readings. The maximum recommended length is 100ft (30m) of 2-conductor 22-gauge stranded wire ACR C/N 31-0007. Use shielded cable and connect on the Data Loggers end to the Common terminal along with one of the conductors. Soldering the wires is the best option.

EH Series RH & Temperature Probes

These Relative Humidity and Temperature probes use capacitive and resistive sensors. Since the conductor’s capacitance and resistance are proportional to length, there is a limit to the length of cable used. The maximum recommended length is 100ft (30m) of 4-conductor 24-gauge stranded cable with a shield ACR C/N 31-0006. Replace the 3ft (0.9m) cable using a flat blade jeweler’s screwdriver connecting the shield to the Common terminal of the Data Logger.

Thermocouple Wires

These Temperature sensing wires generate voltage proportional to the temperature differential from either end of the cable. The maximum recommended cable length for the 20 gauge T/C wire is 300ft (100m). It is not recommended to use regular cables in extending thermocouple wires. The extension wire should be of the same type (K, J, etc.) as the sensor leads. Using any other type of wire will introduce a thermocouple junction. Measurement errors are caused by thermocouple junctions.

IC/LIC-102 Interface Cables

The IC-series Interface Cables may be extended with as many as ten CB-020 20ft (6m) Extension Cables to a maximum recommended length of 200ft (60m).

What is the maximum Cable length between a Computer and a Data Logger?

It depends on the type of computer port and quality of cable. For a Data Logger to wake up and work properly, (when you open the Connection to start communication), there has to be at least 4.5VDC present between the tip and base of the plug at the Data Logger end. If communication proves unreliable, simply reduce the Baud rate thru software. Up to 3 SmartReader Plus Data Loggers can be attached with a Modular Cable system up to 1000ft (300m) w/o a Power Supply

Testing the Communication Cable after Extension

Open the communication port and use a voltmeter to check the voltage between the tip and base of the plug at the Data Logger. If the voltage is below 4.5 VDC, add a Y-Adapter (YA) and a Power Supply (PS) to boost the line. For Stereo Cable systems, purchase YA-200 C/N 01-0098 and PS-201-EU C/N 01-0164 or PS-201-NA C/N 01-0165 for 220VAC or 120VAC respectively. For Modular Cable systems, buy PS only.

Applying MKT as a Compound Line

Applying Mean Kinetic Temperature (MKT) is simple using ACR TrendReader Software – the compound Line function is easy to implement and can be modified to suit any application.Download Calculating Mean Kinetic Temperature

Calculating Average Values is easy with ACR TrendReader Software – the Compound Line function makes it simple to determine the running average or the arithmetic mean for a time interval.

Average values are often used when a signal is fluctuating such that it is hard to determine the overall picture of what is actually occurring. A running average takes into account large transgressions as it moves along the data set so every previous reading affects the latest value calculated on a weighted basis. The arithmetic mean is finite as it can be calculated on a fixed interval of data. Alternatively, the entire data set can be acted on using the sum divided by the size as given by Mean Average in the Statistics given for the graph in TrendReader.

ACR Technical Document-Average Value Calculations.pdf

To reassign comports, you will be accessing Device Manger in Windows. Simply close the ACR software if it is running and follow the steps below:
  1. Click on the Start button and select Settings –> Control Panel.
  2. Double click System and select the Hardware tab –> Device Manager.
  3. Select – Ports COM & LPT to see a list of the com ports assigned to devices in your system.
  4. If the installation went correctly, the cable you installed should appear in this list with its current COM port assignment.
  5. Right click on the device and select Properties.
  6. Click the Port Settings tab then click Advanced.
  7. Click in the COM Port Number menu and select, preferably, an unused port that is in the range for the software you are using. (Note: If all of the ports are labeled in use or used, you may need to assign over one of them. This will create a potential conflict error by Windows, but continue by selecting the port anyway and see if there is an actual conflict. Some times ports are reserved and apparently not used so it is not likely that you will experience an actual conflict.)
  8. Click OK and close out Device Manager.
  9. Restart the ACR software and try accessing the newly assigned port.
The IC 102, LIC 102 and USB to Serial adaptors are USB devices and have drivers that must be installed in the computer in order to allow them to function with the computer. This driver installation process involves two parts:
  1. It installs the components that allow your computer to recognize the cable as a USB device on your system.
  2. It creates a virtual serial (COM) port for your software to communicate through. Windows will assign this virtual COM port based on the available and unused ports in the computer. Typically Windows has 256 ports available. These devices usually are accompanied with a CD or a link that contains the driver.
ACR has several software packages of differing vintage and there may be limits on the COM ports that are accessible through the respective ACR software packages. Most of the installation difficulties encountered will be with the older ACR software packages.
  • TrendReader 3 is the only software that potentially allows access to all 256 COM ports available in Windows. It also has the drivers for IC 102 and LIC 102 contained in the software itself. The software should recognize these cables automatically when plugged in.
  • With EventReader for PowerWatch software, you will need to install the drivers and virtual ports utilizing the CD, thumb drive, or links that comes with the respective interface cables. The drivers are also available on Windows Updates.

You can manually assign COM ports. This process is quite simple to perform. (See “How do I to reassign COM Ports” in the FAQ section

*Also note that any software (ACR or otherwise) that opens a serial COM port will prevent access to that port from additional software while it is running. It is usually a good rule of thumb to close any other software that is communicating through a port before launching any ACR software.

If you are running WIN 7 it is likely the computer does not like the virtual COM port that the cable uses when it installs. Try switching it over to a purely USB connection. Plug the cable into a USB port, close the TrendReader software and do the following:

  1. Go to Device Manager and see if the ACR IC-102 is listed under Ports COM & LPT. If it is, go to step 2.
  2. In device manager again, under Universal BUS Controllers (at the bottom) the ACR IC-102 should be listed. Right click on it and select Properties.
  3. Click the advanced tab.
  4. Uncheck Load VCP – click OK.
  5. Unplug the cable from the USB port. wait 5 seconds, then plug it in again.
  6. Test the connection now in TrendReader as normal

You may need to restart the computer (restarting will help to clear things out). Restart TrendReader to make sure the problem has been cleared up.

  1. Make sure that the channels are active and correct equation numbers are selected (Equation 71 for the RH channel and equation 45 for the temperature channel)
  2. Check the real-time temperature readings of the internal temperature sensor on the logger and see whether it changes if you heat it up by blowing on it or putting your finger on it.
  3. Allow the sensors to reach equilibrium before taking readings
  4. Check the calibration card of the logger and make sure that correct calibration values (Low, Mid, High) are saved on the logger.
  5. Note that the accuracy of the SR2 logger (RH channels) is 4% From 10 to 90% and temperature range of -20C to 40C ( -4F to 104F) and that of the SRP2 logger is 3% From 10 to 90% and temperature range of -20C to 40C ( -4F to 104F).
  6. If the logger was calibrated more than a year ago, it requires calibration. Contact ACR Systems Inc. to arrange for sending the logger for calibration or proceed with the calibration of the logger as is explained in the Appendix B in the Reference Guide.
  1. Make sure that you are using the correct equation numbers.
    The correct equation numbers for the SRP5 and SRP6 loggers are:
    J type thermocoupleEquation 50
    K type thermocoupleEquation 52
    T type thermocoupleEquation 54
    S type thermocoupleEquation 74
    E type thermocoupleEquation 90
    Do not use equation numbers 49, 51, 53 and 73 with SRP loggers.
    The correct equation numbers for the SR5 are:
    J type thermocoupleEquation 50
    K type thermocoupleEquation 52
    T type thermocoupleEquation 54
    S type thermocoupleEquation 74
    The equation number for the Internal Temperature channel should be 45.
  2. Make sure that the “Low”, “Mid”, “High” calibration values are correct and are exactly the same as that printed on the calibration card of the logger.
  3. Always give the logger enough time to come to equilibrium). It is recommended that the logger be placed in an environment that is not affected by rapid temperature swings or changes.
  4. Note: As long as the readings of the logger are within the accuracy specification then there will be no problem. For example: to have correct readings, if you are moving the logger from outdoors to indoors, let it sit for a while until the logger’s temperature comes to equilibrium and then start readings. (Note that the internal thermistor is for cold junction compensation and if the logger is carried from outdoors to indoors, you should give the ng as the readings of the logger are within the accuracy specification then there will be no problem. For the accuracy specification of these loggers refer to the related sections.
  5. If you have extended the cable of the thermocouple, make sure that the connection is secure. Any loose connection results in incorrect readings.
  6. Use ungrounded thermocouples to prevent grounding loops.
  7. Ensure that the tips of the thermocouples are not conducting between themselves. They must be insulated or electrically isolated from each other.
  1. Make sure that correct equation numbers are used.
  2. If you are connecting more than one transducer to the logger, make sure that there is no grounding loop. SRP7 has four common inputs (Labeled “Common”). SR7 has two Common inputs (Labeled “Common”). The Common inputs on the logger are not isolated from each other and can be used as the negative “-” connection for the power supply (or battery) and any of the transducers being logged by these loggers. These common channels are all connected internally. A grounding loop can occur when there is more than one path to ground in your logger-transducer circuit. Ground loops can damage your logger as well as your transducers. To avoid ground-loop problems in your SRP7 circuit:

* Do not use more than one grounded power supply to excite your transducers

* Do not connect your logger to your computer for real time readings unless your computer is battery-operated (i.e. not grounded) or your transducer power supply is not grounded. If you must use more than one grounded power supply in your logger circuit, each transducer you use must be isolated. If you must use non-isolated transducers, then you must use a Signal Repeater/Loop Isolator between the transducer output and the logger.

Yes, you can log the status of a switch and establish if it was opened or closed (on/off) and for how long it remained in each state.
Yes, you can. A SmartReader Plus 4 can be used for this purpose.
You can sample as fast as 1 second with no external power being required. (You can sample as fast as 40 milliseconds with external power applied).
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