What is Chatter?
Chatter is an event that can occur in response to shock vibration. It is detected in the mechanical relay or contactor of the device under test.
When a relay is not energized, its contacts are described as some combination of “normally open” and “normally closed.” When it is subjected to a large shock event like an earthquake, the electromagnetic coil used to hold the contacts in the energized position and the spring tension used to hold the contacts in the de-energized position must be strong enough to withstand the force of the event. Otherwise, a chatter event can occur, leading to disconnection, wear, or damage.
Engineers can re-create chatter events in a laboratory setting by mounting the relay or contactor in the recommended position, simulating a shock test or earthquake, and monitoring the test. Any change in the contacts’ voltage will indicate a chatter event. The engineer can then evaluate the results to determine the contacts’ effectiveness in the case of an earthquake or other shock event.
The VibrationVIEW Chatter Monitoring software package detects chatter events. The software uses the RecorderVIEW package to record the test’s inputs. It then evaluates the recording to determine if a chatter event has occurred. After the evaluation, a dialog box will appear that shows each event that was detected. This information allows the user to evaluate each event and create a chatter report. The user can also post-process recorded files (.vfw) using the Chatter Monitoring software.
With RecorderVIEW, there’s no need to buy extra equipment to collect data. The VR9500 and VR10500 controller hardware can connect to a notebook PC and function as a portable data acquisition system. Record field acceleration measurements directly to the PC’s hard drive. Plus, access all the features of the VR9500/VR10500 including a low noise floor, 24-bit resolution inputs, built-in accelerometer constant current supply, TEDS transducer interface, and a unique DC offset that allows a measurement to true DC with constant current type accelerometers.
Then, employ the VibrationVIEW software to set up and monitor vibration tests with the collected data.
Earthquake Testing in VibrationVIEW
Chatter monitoring is of particular interest during earthquake testing. Structures and equipment installed in seismically active regions must be designed to protect the operating equipment in the event of an earthquake. With the VR9500/VR10500, the user can perform single/multi-axis earthquake tests that meet standards using an earthquake test template or user-defined time transient.
VibrationVIEW runs earthquake simulations with the User-Defined Transient option. There are two methods of creating an earthquake simulation: via template or import.
User-Defined Transient Webinar
Types of Chatter Events
A chatter event is typically characterized as a bounce or discontinuity. A discontinuity is a significant deviation from a monitored parameter. A bounce occurs when the normally open contact does not make a secure connection when the electromagnetic coil is energized.
If the current draw overloads the contacts when the coil is energized, then a perpetual bounce cycle can start. This cycle looks like several moments of contact and loss of contact. This type of chatter event can cause severe damage to the contacts because the electrical charge will jump across the short gap between the contacts and cause extra wear and damage. Contact bounce is a common problem in motor contactors that are not the correct size for the equipment.