SL900A datasheet(79/103 Pages) AMSCO

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[v1-12] 2018-Oct-29

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SL900A − Shelf Life Calculation

Low Battery Flag

The Low Battery flag is a register bit i.e. volatile memory. The

Battery status is checked during logging immediately after a

Start Log command is received even if no ADC conversion takes

place and also before each logging event. It is also checked

when a GSV command is received.

If the battery level is below the PORHL level the low battery flag

is set and any logging in progress is stopped, but the RTC is still

running. See Figure 60 for PORHL thresholds. The Low Battery

status flag is only set as a result of a battery status check and

not if a PORHL occurs at another time.

Shelf Life Algorithm

The following is a C language representation of the shelf life

algorithm, implemented in SL900A.

At startup of logging:

SLcurr (22 bits, signed) = SLinit << 6; // multiply by 64

SLerrlo = 0;

SLerrhi = 0;

At each temperature logging event:

Tdiff (10 bits, unsigned) = Tmeas (10 bits, temperature

value) – Tinit;

Tindex (8 bits, unsigned) = Tdiff >> 2; // divide by 4

if (Tdiff > 236) {SLerrhi++; Tindex = 59}

if (Tinit > Tmeas) {SLerrlo ++; Tindex = 0}

Counter (8 bits, unsigned) = 0;

While (Counter <= Tindex)

{

SLdec (8 bits, unsigned) = P[Counter];

SLcurr = SLcurr – SLdec;

Counter++;

}

if (Tindex & (Tindex < 59)) // Interpolation process

{

SLdec++; // compensate for truncation

if (Tdiff & 0b00000010) {SLcurr = SLcurr – (SLdec

>> 1)}

if (Tdiff & 0b00000001) {SLcurr = SLcurr – (SLdec

>> 2)}

}

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