# SAM Consumables

A SAM consumable is defined as any piece of hardware in the SAM
instrument that has a limited lifetime or a metric worth tracking. What
exactly \"lifetime\" means is dependent on the specific piece of
hardware we are interested in and a single consumable may have more than
one way to define its lifetime. This page details the logic we use to
extract the data for each consumable. Note that this is the master
reference, which means the engineers and scientists should ensure that
the logic detailed here is correct. All consumable data is available on
XINA Online at <https://ssed.gsfc.nasa.gov/xina/xo/tool/sam-timeline>.

## WRP

### On Time 

WRP on time is determined by calculating the total time that WRP HKIDs
334:WRP1 PWM, 336:WRP2 PWM break the threshold value of 50 for a TID.

## Helium

### He 1 Pressure 

He 1 Tank Pressure is a reading of the current pressure; it is not a
consumable where metrics are added between TIDs. The current He 1 Tank
Pressure is calculated from PRES_1_He1 and T47_He_1 (HKIDs 89 and 43).

Because gas pressures are temperature sensitive, the pressures were
temperature corrected to room temperature (22 degrees Celsius): Pressure
= PRES_1_He1 / (T47_He_1 + 273) \* (22 + 273).

### He 2 Pressure 

The He 2 Tank Pressure is a consumable recorded as a loss of pressure;
it is a consumable starting at 2.3K psi and each TID records the amount
of pressure lost. The He 2 Tank Pressure is calculated using regular
expressions to measure Valve 33 and Valve 34 Open Times.

The loss in pressure is then calculated: Loss = (V33_on_time +
V34_on_time) \* .004 psi/sec.

## O2 Gas 

### On Time 

O2 Gas On Time was calculated using regular expressions to look for the
quick opening and closing of Valve 35. Each time this event occurred,
.02 seconds were added to O2 Gas On Time.

## Cal Gas 

### On Time 

Cal Gas On Time was calculated using regular expressions to look for the
quick opening and closing of Valve 36. Each time this event occurred,
.02 seconds were added to Cal Gas On Time.

## TEC A & B 

### On Time 

TEC A & B on times were determined using regular expressions to look for
when the heaters corresponding to each TEC (A:61 \| B:62) were open loop
or off. The on time was determined by subtracting the ON time from the
OFF time and summing all of these differences for a TID.

### Cycles 

TEC A & B on times were determined using regular expressions to look for
when the heaters corresponding to each TEC (A:61 \| B:62) were open loop
or off. Each time a heater switched from ON to OFF, a cycle was added to
the corresponding TEC.