VR2 Troubleshooting

Q1. Why does my data file indicate;
*Flash memory failure in block 4
*End of block 4

This message should only occur in VR2 firmware versions 1.00 to 1.02. This message indicates that the memory block 4 is corrupt and the PC/VR2 software is not able to read the data. The condition that causes this error message is a result of an expired battery. When the VR2 battery expires the microprocessor resets the memory pointer to an incorrect location causing a Read data checksum error. The PC will download all the memory data in the VR2 (2 Mbytes). The memory may contain data from previous deployments along with the data from the current deployment. Contact VEMCO for a more detailed explanation.

Q2. I downloaded data from 2 VR2s that were both in the range of a test tag. I noticed that the detection times for the same ID code were different between the 2 receivers and the difference increased over time. Why?

This is because all VR2 time clocks are not created equal. This is a function of the clock oscillator in each VR2. Vr2 clocks can drift over time.Each VR2’s clock can drift 4 seconds/day (time drift based on manufacturer specifications). When a VR2 is initialized the PC software sends the Date and Time of the PC clock to the VR2. The VR2 stores this time in memory. The VR2 “runs” and starts its transmitter detection function. The VR2 advances its internal clock each second. When a tag is identified the VR2 stores the actual date and time in memory along with ID code. Let us give 2 VR2s time drifts of +2 and –2 seconds/day respectively. After 4 months deployment, the 2 receivers will be 8 minutes apart. Near the end of the deployment a tag identified by both receivers at the same time will have detection times 8 minutes apart.

When you download data from a VR2, the PC software creates a data file in your data directory. The data file consists of detections with Date and Time. When data is downloaded the VR2 sends its clock time to the PC. This time is stored in the top of the data file and the PC stores its clock time in the data file as well. The VR2 start time, VR2 Stop time and PC Stop Time can be used to correct for time drift. If detection time is important to you then you must calculate a corrected time and date for each receiver. You must assume a linear value for time drift. Contact VEMCO for a sample XLS file that illustrates how to correct for time drift..

*08, StartTime(yyyy-mm-dd,hh:m:ss)
>08,2003-10-09, 10:56:55
*09, StopTime(yyyy-mm-dd,hh:m:ss)
>09,2106-02-07, 06:28:15
*15, PC Time at download(yyyy-mm-dd,hh:m:ss)
>15,2004-10-08, 09:19:03

Q3. When a VR2 is initialized does it erase previous data?

ANSWER
When a VR2 is initialized it resets its internal memory pointer to the beginning of memory. Data is not erased. As the VR2 records detections it writes over previous data in memory.

Q4. What is my VR2 firmware version?

The firmware is an industry term that applies to the software program that is executed by the VR2 internal microprocessor. When we make programming improvements to the VR2 microprocessor we re-name the firmware. The original VR2 firmware is version 1.00. The current firmware version is 1.04. Occasionally it is necessary to update the internal software program. The firmware version is indicated in the HEADER of all VR2 data files.

*04,VR2 Model
>04,VR2-069.0k-1.02-2-1432-D(SN1754)
The firmware version of VR2 with serial# 1754 is 1.02

Q5. Are VR1s and VR2s compatible?

Both models can detect R256 transmitters. VR1s are not capable of detecting R04k, S256 and R64k transmitters.

Q6. What does “Checksum invalid” in a data file mean?

“Checksum invalid” is a report of the number of almost complete tag transmissions that are rejected by the receiver’s error checking algorithm. VEMCO receivers are very rigorous and only accept transmissions that pass through several checks.

Q7. What does “Total syncs” in a data file mean?

The Sync interval is the time between the first two pings of a coded tag’s transmission. The VEMCO receiver determines the code type of an acoustic transmission by measuring the time between these two pings. The receiver records the number of correct sync values it receives.

Q8. What does “Total detections” in a data file mean?

The “Total detections” value is the number of complete coded ping trains received. A train of pings can be received but fail the strict validity test and not be accepted as a correct ID number. A ping train that is not accepted is not counted as a detection but the individual pings will be counted in the “Total pulses received” value.

Every acoustic ping that is detected by the VEMCO receiver is added to the “Total pulses received” value and is stored in memory. This value represents a very crude estimate of the receiver’s function during deployment. If the “Total pulses received” value is very high and the “Total detections” value is low then one could attribute this difference to:

1. high noise in the environment and/or
2. tag collisions and/or
3. poor detections due to missed pings from low signal levels or acoustic multipath transmissions