Frequently asked questions
1. What is A Data Logger & What Is It Used For?
A data logger or datalogger is an electronic device that is used in conjunction with a computer to monitor or record various signals.
Remember when you were at school and you did experiments, measuring the temperature of boiling water, taking a reading every minute until it boiled. Well, a data logger would do this for you automatically. All you need to do is put the sensor in the water and tell the data logger how often to take a reading and at the end of the experiment, you download the information to the computer and it will produce a graph for you.
The data logger may have internal sensor(s) so it measures where it is located or it may have one or a number of channels where external sensors can be connected. Some data loggers can be configured to accept a wide range of sensors.
Using the computer, the data logger is programmed to "wake up" at predetermined intervals, take a reading and go back to sleep. The time period between readings is called the "sample period" and can range from many readings per second to once per day. The data logger will have an internal memory where the readings are stored. Once this memory is full, the data logger can be programmed to stop taking new readings, and therefore not loose any readings or, overwrite the oldest reading.
Once the data logger has been monitoring for the required time period, it is connected to the computer. The stored readings are then downloaded and saved on the computers hard disk. A graph can now be produced showing the measured signal over time - providing an accurate account of what the data logger measured - useful for proving a shipment got too hot in transit or that your office is too hot to work in!
Once the stored information has been downloaded from the data logger, the memory is cleared and the data logger is ready to be re-used over and over again - well, until the battery runs out, which is usually a number of years.
The majority of Signatrol's data loggers are battery powered and all have a battery life of at least 3 years.
Where Are Data Loggers Used?
Data loggers are used in a wide variety of applications from simple monitoring of temperature in an office environment to monitoring the temperature of perishable products in transit or optimising the production process of food, pharmaceutical or engineering products. The same data logger can be used in a variety of applications, if you want to make a record of temperature, humidity, pressure or Voltage and current signals, we have a data logger to suit your needs.
This is a typical graph that you would get from a Signatrol data logger. It was produced by our graphing software - TempIT ( pronounced "temp it") although some functions shown are only available in the PRO version:
2. What is response time?
Nothing responds in zero time and the response time is a measure of the time that a particular sensor takes to reach the equilibrium of the environment it is placed in. The response time can therefore be defined as the time required for a sensor output to change from its previous state to a final settled value within an acceptable tolerance band. Because sensors generally respond exponentially, they never actually reach their final value they just get closer and closer asymptotically until they are so close as to be regarded as settled. This can be an arbitrary value (say 99% of the change) or the point at which they are so close as to be within the tolerance of the sensor. This is further complicated because there are two generally accepted ways of stating response times i.e the 63% and the 10-90%. The 63% figure is called the time constant and is the time for the sensor to reach 63% of its final value. As a rule of thumb the sensor reaches 95% of its final value in 3 time constants and 99% in five time constants. The 10-90% is the time it takes for the sensor to traverse between 10% and 90% of its final value.
Signatrol have incorporated some advanced software techniques in our TempIT software that can remove thermal lags caused by putting our SL50 series data loggers in waterproof enclosures. Call our sales office or submit an enquiry form for more details.
3. Using TempIT In Secure Applications.
TempIT can be used in FDA 21 CFR Part 11 applications if your procedures are written with TempIT in mind. Here we have a document that explains how each requirement can be accomplished.