Set Up Sampling Rate

Experiment files and auto-ID sensors set up parameters for data collection. Most often you will not need to change the data-collection rates that are loaded. However, the rate can be manually set when Time Based is selected as the mode in the Data Collection dialog.

Changing the Sampling Rate

The appropriate sampling speed is one that is fast enough to capture all rapid changes in the measured quantity, but that does not generate an excessive number of points. For example, to study the motion of a mass spring system with a 1 second period using the motion detector, you would want to use a 40 or 50 samples per second to catch all the details. With a temperature probe which can take several seconds to reach a new temperature, anything faster than 1 or 2 samples per second would generate many nearly identical data points.

To set an appropriate sampling speed:

1. Consider the response time of your sensor and the rate at which conditions change in your experiment. Decide on a sampling speed somewhat faster than the shortest change you expect, subject to the requirement that you don't want to gather too many points.
2. Choose Data Collection from the Experiment menu, then enter values for the Sampling Rate. You can enter a rate (samples/second) or an interval (seconds/sample) and the other value will be updated automatically. For example, if you enter a rate of 10 samples/second, the interval will be updated to 0.1 seconds/sample. Note: If the requested sampling speed exceeds the recommended sampling speed for a particular sensor or for the interface, a message will appear in the dialog. Logger Pro will still allow you to exceed the recommended sampling speed for a sensor. See below for more information about maximum data collection rates.
3. Click Done to save your changes.

Maximum Data Collection Rates

The maximum data-collection rate depends on the interface and number of sensors being used.

LabQuest or LabQuest Mini

A single analog sensor can collect up to 100,000 samples/second

2 or more sensors can collect up to 10,000 samples/second

LabPro

A single analog sensor can collect up to 50,000 samples/second

2 sensors can collect up to 5000 samples/second

3 sensors can collect up to 3333 samples/second

4 sensors can collect up to 2500 samples/second

Note: If you are using a LabPro and your sampling speed is 250 samples/second or faster, the data table and graph will not be updated until data collection is complete. In this case, if you stop data collection before it finishes, no data will be returned from the interface.

WDSS

3 or fewer sensors can collect up to 1000 samples/second

4 or 5 sensors can collect up to 500 samples/second

Go! Temp

2 samples/second

Go! Motion

50 samples/second

Go! Link

200 samples/second

OHAUS balance

1 sample/second

GPS

1 sample/second

Spectrometer

1 sample/second

Motion Detectors and Undersampling

If you are using a Motion Detector and an analog sensor with a sample rate faster than the maximum for the motion detector, Logger Pro will set up the sampling rate of the analog sensor to sample at the higher rate and the Motion Detector to sample at a slower rate. Undersampling is automatic and requires no user settings; this is also called Collision Mode.