What Is a Pulse Logger?
A Pulse Logger is an instrument or device that records a time series of signals that occur rapidly over a short period of time.
By digitally converting signals sent from sensors usually connected to a detector, it can automatically record them as data over time. It is used to analyze events.
Therefore, it is not used alone. It can be incorporated to count the number of signals per unit time sent from a rotating counter, such as a flow meter or an anemometer, to determine its volume and speed.
Uses of Pulse Loggers
Since pulse signals output according to speed or quantity can be digitally converted and recorded, a unit conversion device and a detection device can be incorporated according to the purpose of measurement. It is possible to calculate water, gas, and electricity usage, rainfall, and wind speed.
Pulse Loggers only function to count pulse signals in a time series, but they have less deterioration over time than analog loggers and have excellent preservation properties. Due to their continuous and long-term use, pulse loggers are also used for various environmental measurements at research institutes.
Principle of Pulse Logger
1. Conversion to Digital Signal
Analog signal outputs such as contact signals and DC voltage signals generated by a revolution counter are converted to digital signals through a signal converter and counted. The counts are then continuously recorded in data memory at set time intervals.
By multiplying the number of counts per hour by a factor that matches the measurement objective, the recorded data can be calculated according to the measurement unit. Pulses are not time-stamped, but are recorded in data memory based on the time they occur.
2. Pulse Signal Measurement
If the frequency is f (Hz) and the period is T (sec), the relationship is f = 1/T. Therefore, the data to be measured can be obtained by measuring either of them. Pulse Logger has the following two types of pulse measurement methods:
Direct Method
In the direct method, a fixed time is set for the gate pulse, and the number of pulses to be measured within the gate pulse is counted. The direct method directly measures frequency.
Reciprocal Method
In the reciprocal method, the pulse to be measured is the gate pulse, and a clock signal set to a specific frequency is output. The signal period is obtained by measuring the number of clock signal pulses relative to the gate pulse. Therefore, the reciprocal method measures frequency from the reciprocal of the period.
How to Select a Pulse Logger
1. Difference in the Number of Counts
The method used for measurement is the direct method using frequency (Hz) if the number of counts of pulse signals output per second is large. When the number of counts is small, the reciprocal method is often used, which uses a period based on the length of time per round trip of the pulse signal that is output repeatedly.
2. Difference of Methods
For measuring instruments with short-period time lengths, the number of data points increases and accurate values can be recorded, but it is difficult to recognize short-period data that exceeds the sensitivity. Conversely, if the time length is set to long-period, the instrument cannot measure pulse width or detect short-period pulses because there is no pulse signal within the set measurement time.
Therefore, considering whether the purpose of measurement is short-period or long-period, it is required to select a device with a measurement method that matches the pulse signal strength, data collection period, and the amount of pulse counts, and to adjust the set value.
Other Information on Pulse Loggers
Examples of Pulse Logger Applications
One example of Pulse Logger use is for measuring the rotation speed of copier rollers. The purpose is to measure the number of roller rotations for operation verification in research and development.
By using a temperature measurement unit and acceleration measurement unit at the same time, it is also possible to inspect radiated heat and operation defects of each part. Measurement data can be transferred to a PC via a network for simultaneous measurement and verification.