“I am getting the error message “Internal error $4:USB.0012345” / “LogTag failed to respond [20]” – what do these mean?”

“Internal error $4” and “LogTag failed to respond [20]” are very general error messages which simply mean that LogTag Analyzer found an interface and detected the presence of a LogTag product inside the interface, but was unable to establish communication. The letters and numbers after $4 represent type and serial number of the interface. Often this error will disappear by simply repeating the action you were performing when the error occurred, but sometimes it can be a bit more difficult to locate the cause. Here are some scenarios in which these errors could occur and what to do to rectify the issue:

• There is poor electrical connection between the LogTag contact pads and the interface pins; this can happen if the contact pads are dirty or have been exposed to a corrosive environment. Usually this can be corrected by cleaning the contact pads on the LogTag^®. Use a soft, damp cloth. For stubborn stains you can also use a soft pencil eraser.
• There is a “stuck” contact pin inside the interface; look inside the slot, there should be three contact pins visible, they should slide in and out with moderate resistance when force is applied (e.g. with the end of a pencil). Make sure all pins move freely.
• There is not enough power being supplied to the interface (USB); We have seen this error when USB interfaces are used on unpowered USB hubs with other equipment also connected. USB ports have a limited ability to supply power and we would always recommend to connect the USB interfaces directly to the computer or to use a powered hub.
• Communication has been interrupted prematurely; sometimes a user will remove the LogTag^® from the interface too early, which will cause this error to be displayed. In this case simply re-do the action with the LogTag^® connected properly throughout the communication.
• The USB port is defective; Try a different port and see if the error persists.
• The LogTag’s battery is critically low
• The LogTag has just been removed from a cold environment. Lithium cells and in fact all batteries typically exhibit a lower battery voltage in cold conditions, sometimes significantly lower, so downloading units that have come e.g. directly out of a freezer could show communication problems. In that case it may pay to wait until the unit has acclimatised to room temperature or slightly above.
• There was water in the unit; different LogTag^® models have different ingress protection and are not waterproof. If water got inside the unit, it will keep working for a time, but eventually the communication will cease to work.
• The LogTag has been subjected to strong EMC fields or radiation, causing a corruption in its internal memory.