If your Nortek instrument does not last as long as indicated by the calculated time in the deployment, this may indicate that the instrument draws too much power. Different batteries can have different total power. Here it is assumed that you use Nortek supplied batteries, which is according to the calculated time in the deployment. You should use a dedicated multimeter when you do these measurements, the current and voltage measured by your power supply is probably not accurate enough to get a good result.
We have different platforms that draw different amounts of power. AquaPro, Aquadopp, Vector: if the serial number of your instrument is greater than 5000, you have a midlife instrument. Less than 5000, you have a pre-midlife instrument. AWAC: If the serial number of your instrument is greater than 1000, you have a midlife instrument. Less than 1000 indicates you have a pre-midlife instrument.
The amount of time the instrument has been connected to power, does effect the current measurements in this test. The instrument is equipped with a means of keeping the time correct between measurements. A circuit in the instrument a Real Time Clock (RTC), keeps the time correct. The RTC has either a battery or a capacitor, to keep a constant flow of current to the RTC. If your instrument has been disconnected from the power source, the RTC will use up the power in the internal capacitor or the internal battery. When you do connect the instrument to power again, the internal battery, or capacitor will draw power, also in power down mode. A midlife card that has not had power for some hours, can draw 1-4mA at 15V in power down mode, without there being anything wrong with the instrument. To get the correct power drawn, indicated in the matrixes below, your midlife-instrument may need several days on power. For pre-midlife instruments, you need something like 10-15 minutes until the capacitor is fully charged, and you should get the power indicated in the matrix below.
The type of communication used (RS232 or RS422), does also effect the amount of current drawn in different modes.
Here is a simple test to check if your Nortek instrument draws too much power
Go to Terminal Emulator and send a break. Dependent on the type of instrument you have, you should get an answer from the instrument similar to this:
To set the instrument in Wait Mode, you type WM in the command window of the Terminal Emulator, and press send. For the WM-command you do not get an answer from the instrument, but you can see the current the instrument draws, decreases after a few (5-10) seconds. Read the current your instrument draws, and compare with the correct matrix. Send a break in the Terminal emulator to get your instrument back in command mode.
To set the instrument in Power Down mode, you type PD in the command window of the Terminal Emulator, and press send. You should now get an answer from the instrument like this ¶¶. Read the current your instrument draws, and compare with the correct matrix.
For more about this, the Troubleshooting Guide is worth a visit.
Power drain figures