Table of Contents

  1. What is a data logger?
  2. What does 8-bit, 12-bit & 16-bit mean?
  3. What resolution should I use?
  4. How long will the battery last?
  5. What is a thermistor?
  6. What is pulse recording?
  7. What is event recording?
  8. What is logic level recording?
  9. Will you make a 'special' data logger for us?
  10. What is a look-up table?
  11. Will you make a 'special' look-up table for us?
  12. What is relative humidity?
  13. What is Dewpoint?

Please send us a question if you cannot find the answer here.


  1. What is a data logger?

    In the general sense a data logger is any device that records (logs) data. The device does not need to be electronic but usually is nowadays. Before electronic recording techniques were developed data was either recorded by hand on a log or automatically on a chart e.g in a barograph. Modern data loggers are generally smaller, more accurate, require little maintenance and have sufficient memory for a great deal of readings. Modern data loggers will usually consist of: a connection to a sensor (either internal or external); an analogue to Digital Convertor to convert the output of the sensor to a number; memory to store the data; a real time clock (RTC) to keep the time; and a microprocessor to control everything. Additionally most models of data logger including Zeta-tec's will have an interface to a PC to enable configuration and offloading of data. This interface has often been RS232 but now often utilizes the USB.

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  2. What does 8-bit, 12-bit & 16-bit mean?

    In basic terms this refers to the length of the number that can be used to store a reading. 8-bit etc. refers to binary values but if we were using normal decimal nos we might say 2-digit or 4-digit. 2-digits nos. can store values between 0 - 99 - this gives a resolution of 1 part in 100. 4-digit can store nos. in the range 0 - 9999 giving a resolution of 1 part in 10,000. Computers and a Zeta-tec data logger use binary nos that store '1's and '0's and an 8-bit no. can store values between 0 - 255, 12-bit 0 - 1023 and 16-bit 0 - 655535 giving a resolution of one part on 65536 or 0.0015%.

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  3. What resolution should I use?

    Generally we would always say that higher resolution is better. However higher resolution uses more memory and 16-bit uses twice as much memory as 8-bit. If you are carrying out long term or detailed logging operations this might be an issue. Having said that, our USB data loggers have sufficient memory for over 65,000 readings.

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  4. How long will the battery last?

    This is a difficult question. If you set up a data logger to take a reading every three hours the battery would last at least five years, however if you were using the RVIP logger to monitor a switch and had set the logger to supply the current through the switch then the battery could (theoretically) be flat in a month. We certainly have customers that leave our data loggers operating for many months, however if you are about to carry out some critical logging for an extended period then please change the battery. We generally say change the battery every two years but as you can see the situation is complex.

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  5. What is a thermistor?

    A thermistor is a resistor whose resistance varies with temperature. A thermistor can have either a positive temperature coefficient (resistance increases with increasing temperature) or a negative temperature coefficient (resistance falls with increasing temperature). Older design thermistors were crude devices that could only be used to detect large temperature changes but modern manufacturing techniques have realised the production of high accuracy devices. It is these devices that are used in our thermistor probe. Thermistors have two main advantages for measuring ambient temperatures(1) they are relatively inexpensive (2) they have large changes in resistance for a smallish change in temperature, this allows the use of relatively inexpensive interface electronics and few problems with sensor leads. They do have a quite complex relationship between temperature and resistance (Steinhart-Hart equation) but this is all taken care of in our resistance data logger.

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  6. What is pulse recording?

    Pulse recording - as we use the term with our RVIP data logger - means recording a stream of pulses. For example, to record pulses per second set the logging frequency to one second and all the pulses within that second will be counted (up to 4000Hz). This feature has been used for example to record engine speed. If you wanted to measure something occuring much less often then you could set the sampling interval to say 12 hours.

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  7. What is event recording?

    Event recording is recording the time of an event for example a door closing, a light comingon or a PIR activating. 'Event' mode is very different from the normal 'measure' mode. Measure mode samples every sampling interval whatever has happened whereas event mode only makes a record if there is something to record. Events are recorded in our RVIP data logger to a resolution of one second.

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  8. What is logic level recording?

    Logic level recording just records whether an input is high or low as opposed to, for example, recording a temperature. For example you could record whether a door was open or closed by using a microswitch connected to the door and the RVIP data logger and set the sampling rate to 5 seconds, then every 5 seconds the logger would record whether the door was open or closed.

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  9. Will you make a 'special' data logger for us?

    We do make specials for some customers. Please email us with a rough specification of what you want and the quantity that you require.

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  10. What is a look up table?

    Data loggers use an electronic circuit to convert a measured value into a number; in the case of our USB data loggers a value between 0 and 65535, the lookup table translates the number into a real world value such as temperature, resistance, humidity etc.

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  11. Will you make a 'special' look up table for us?

    Yes. We may charge for this depending on how much work is involved or how many loggers you are purchasing.

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  12. What is relative humidity?

    Relative humidity is the percentage of the maximum moisture that the air is holding at a given temperature. As temperature increases air can hold more moisture so air contains less moisture at 50% RH at 10ºC than it does at 50% RH at 30ºC.

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  13. What is Dewpoint?

    The dew point is the temperature to which air must be cooled for water vapor in that air to condense into water and form dew.

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