Basic Knowledge of Temperature Recorders

Thermometers such as thermocouples and resistance thermometers are connected to a temperature recorder.The measured temperature is then recorded in the temperature recorder. This section explains the specifications of temperature recorders, how to read them, and the reliability during temperature data collection.

Temperature recorder specifications

When selecting a temperature recorder, you need to understand the meanings of terms written in the specifications. This section explains how to read the specifications of temperature recorders.

Number of channels

Indicates the number of points (channels) from which the temperature recorder can collect data.

Measurement cycle

Refers to the speed at which to sample analog signal information, which indicates at how many seconds one point is sampled. The measurement cycle is also called the sampling cycle.

A/D resolution

The resolution for A/D conversion, which is generally expressed as a number of bits.
If the resolution is 16 bits, a full scale value divided by 2 to the 16th power (65536) is the minimum resolution during A/D conversion.

Input type

Indicates the type of signals that can be input to the temperature recorder.

Maximum input voltage (rated)

The maximum voltage value that can be applied between the + and − terminals of the input without breaking it. The maximum input voltage does not indicate the measurable voltage value.

Input impedance

Indicates the resistance value when a signal is input to the input unit of the temperature recorder.

Measurement accuracy

Indicates the accuracy of the temperature recorder. The measurement accuracy is represented in two ways: FS (full scale, or entire measurement range) and rdg (reading). In general, the rdg representation offers a higher accuracy.
Also, as the actual measurement accuracy, a shift amount is often added as “± XX digit (XX°C/°F).”

Example: The statements “±0.1% of FS” and “±0.1% of rdg” are compared below in terms of the measurement accuracy when “100°C (212°F)” is measured in a K thermocouple range.

  1. ±0.1% of FS  FS = 1572°C (2861.6°F)
    This results in a measurement accuracy of ±0.1% × 1572°C (2861.6°F) = ±1.572°C. (2.8616°F)
  2. ±0.1% of rdg  rdg (reading) = 100°C (212°F)
    This results in a measurement accuracy of ±0.1% × 100°C (212°F) = ±0.1°C (2.12°F).

Reference junction compensation accuracy

This specification indicates the accuracy relevant to temperature measurement using a thermocouple.
A thermocouple measures the temperature difference between two different types of metal junctions (temperature measuring junctions) and the junction on the temperature recorder side (reference junction) and adds the temperature measured at the reference junction to measure the temperature of the temperature measuring junctions.
The reference junction compensation accuracy shows the accuracy of the reference junction temperature.

The table below lists the specifications of a typical temperature recorder.

Specification table
Learn practical methods for installing a temperature recorder.

Reliability during temperature data collection

Since temperature data is generally collected for a long time, the reliability in data collection is an important factor in selecting a temperature recorder.

Operation at an unexpected power-off

When the power supply is turned off unexpectedly (such as due to an instantaneous drop in the power supply), it would be a big problem if the data you have measured so far is lost. To avoid this problem, select a temperature recorder that can protect the collected data even in cases such as this.

The KEYENCE NR Series significantly improves the reliability of measured data saving with our unique algorithm and super capacitor-based micro UPS circuit. This improved reliability ensures complete data saving to the SD card even if an unexpected power-off occurs. The NR Series features a highly reliable design that reduces the risks of data loss and file system damage.

Operation at power supply recovery

It would be inconvenient if, after a power-off due to a problem such as a power supply disconnection, your measurement remains stopped even after the power supply recovers. This issue can be prevented by selecting a temperature recorder capable of automatically starting collection at power supply recovery.

Operation at power supply recovery

The KEYENCE NR Series is equipped with an auto start at power-on function. When this function is set to ON, data collection is automatically started at power-on.

Large-capacity memory

Collection of data for a long time leads to a huge volume of data.
Hence, select a recorder equipped with large-capacity memory or a recorder capable of recording data into external memory.

The KEYENCE NR Series is compatible with a 16 GB SD card.
As shown in the table below, this product enables you to collect data without worrying about the remaining memory capacity even during long-time measurement.

Sampling cycle Sampling frequency Collection period
1 μs 1MHz 1 hr 30 min
10 μs 100kHz 15 hr
100µs 10kHz 6 days 4 hr 30 min
1ms 1kHz 61 days 20 hr 30 min
10ms 100Hz 618 days 12 hr 30 min
100ms 10Hz 6185 days 4 hr 30 min
1秒 1Hz 61851 days 20 hr 30 min

* Calculated by assuming a 15400 MB data area.
* All calculated with the number of channels set to 1.
* Be sure to use a genuine SD card from KEYENCE.
* For the NR-EN16, a collection period of approximately 60% is assumed.
* For the NR-C512, a collection period of approximately 30% is assumed.

How to process temperature data after collection

Collected temperature data is meant to be analyzed.
In addition to measurement functions, important factors in selection also include how easy it is to create reports and similar factors such as whether the necessary analysis functions are provided.

Easy report creation

Ultimately, the collected temperature data is meant to be summarized in a report for analysis. It would be desirable if you could minimize the time spent creating reports, thereby enabling you to focus on data analysis. For this purpose, select a temperature recorder that is highly compatible with PCs (that allows for easy report creation).

Easy report creation

The KEYENCE NR Series is equipped with a real-time Excel transfer function that helps you create reports. At the same time that data is collected, it is directly written into a regular Excel format you usually use. After collection is completed, a report is automatically created, thereby making it easy for you to edit the data or create another report.