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NOTE: To get off this list, send email to majordomo@aqua.ccwr.ac.za with the body of the message containing the line: unsubscribe sowacs I have never fully investigated the function of the lithium battery but the only reason they are normally fitted is to retain data to enable a microprocessor to return to a previous state upon power-up. Thus the battery is only used to provide power to retain the memory when the unit is switched off - it is not used when the unit is running (but see below). For the 1502 I suspect the battery is used to help remember the previous setup so that if you are using the 1502 in its normal manually controlled mode you start with the settings you used from where you left off before turning it off last time. It is also just possible that it retains some internal calibration information but only Tektronix could tell you that - seems unlikely from our experience. If calbration data is not stored and you are resetting all of the setup information after power-up by reloading or resetting the paramters from a PC or logger, then the battery may not be necessary for data retention. However the unit won't start if the battery is not there as the 1502 checks the battery voltage on power-up and refuses to operate if the voltage is too low. As you say could can probably fool the 1502 at that point by feeding in a suitable voltage in place of the battery - a resistor and zener diode would be all you need to do this. The problem with that trick though is that if you want to use the 1502 manually you will have to keep resetting the setup every time you want to use it. Andrew Sandford > -----Original Message----- > Hi Andrew, > > Thanks for the info. I was under the impression that the 1502's do not > require energy from this battery until the unit is powered > up. This being so, there appears to be no good reason to use a battery at > all. I have never fully investigated the function of the lithium battery but the only reason they are normally fitted is to retain data to enable a microprocessor to return to a previous state upon power-up. Thus the battery is only used to provide power to retain the memory when the unit is switched off - it is not used when the unit is running (but see below). For the 1502 I suspect the battery is used to help remember the previous setup so that if you are using the 1502 in its normal manually controlled mode you start with the settings you used from where you left off before turning it off last time. It is also just possible that it retains some internal calibration information but only Tektronix could tell you that - seems unlikely from our experience. If calbration data is not stored and you are resetting all of the setup information after power-up by reloading or resetting the paramters from a PC or logger, then the battery may not be necessary for data retention. However the unit won't start if the battery is not there as the 1502 checks the battery voltage on power-up and refuses to operate if the voltage is too low. As you say could can probably fool the 1502 at that point by feeding in a suitable voltage in place of the battery - a resistor and zener diode would be all you need to do this. The problem with that trick though is that if you want to use the 1502 manually you will have to keep resetting the setup every time you want to use it. Andrew Sandford