This section covers HMI heater zone control under nominal operations. Following sections are for additional information on changing duty cycles or other heater related operations should they be required.
The HMI front window and telescope tube (heater zones 1, 2, and 3) have been under tight deadband control since April 2013. Optical bench temperatures (heater zones 5, 6, and 7) tight deadbands were set in August 2014.
HMI focus varies with the front window and aft telescope tube temperatures (zones 1-3) so adjustments to the deadbands for those zones are made frequently during nominal operations. Note that changes must be reflected in eclipse exit script settings during eclipse season.
Heater zone adjustments can be made either from the "Heater menu" section of the hmi_ops wrapper STOL or by direct command through the EGSE console. Temperature settings are entered in DN when using the direct command and are entered in degrees C when using hmi_ops. Setpoints sent to the instrument are in DN and the STOL uses a Steinhart temperature conversion approximation to determine the proper values. The IDL proc temptocounts.pro can also be used to convert temperatures in degrees C to DN values.
Here is detailed documentation on how to perform HMI thermal adjustments.
The IDL routine thermal_zones.pro will plot HMI heater zones and deadbands. The display may be running and updating itself on the HMI-MON machine.
The routine accepts many different keywords so you can plot in real-time, select zones,
print out statistics and information, plot in DN or engineering units, etc. Sample calls are:
Either the deadbands, or the duty cycle/duration will need to be changed.
Changing the deadbands will not adjust the temperature, it will just keep the
heaters from hitting a deadband and cycling.
Changing the duration or deadband duty cycle will change the zone temperature, and will likely
effect the temperature of other zones as well.
You can use thermal_limits with the /info keyword to check the rate of temperature increase/decrease
so you have some idea of how long it will be until the heater zone is in danger of
reaching the deadband and cycling.
In IDL, you can check what the heater zone in question was doing at the same time in previous years,
and to see what adjustments were made (to DC, DUR, or deadbands) at that time.
To plot the effective DC, find the deadband duty cycle and the duty cycle duration,
then use actual_dc.pro to find the effective DC. You want to do something like this:
On HMI, duty cycles and durations are adjusted to keep temperatures constant, rather than
relying on deadbands, as AIA does. The effective duty cycle depends on the deadband duty cycle
and duty cycle duration, which can be adjusted for each heater zone.
The actual duty cycle can be found using the giant spreadsheet in the JSOC-IOC, or by using the formula:
Actual duty cycle (%) = ROUND(duty cycle/100*duration)/duration
Or by using actual_dc.pro:
IDL> print, actual_dc(dc=19, dur=11)
18.1818
If you want to change the duty cycles, you can use the program dc_helper to calculate new dc and duration
values for a target effective duty cycle. Input format is "dc_helper, dc_guess, dur_guess, target",
where target is the target effective duty cycle, and dc_guess and dur_guess are your best guess for what the new dc and duration should be.
dc_helper needs starting values in order to find an accurate estimate. These guesses don't have to be good guesses,
but should be within +/- 25 of the best value (which is a very broad range). If you are changing the dc or dur
for a zone, the current dc and dur values are more than fine for initial guesses.
If you want to look up past changes in a zone's duty cycle, check the
HMI Thermal History Spreadsheet, or follow this example for zone 7 to see where
and when duty ccles were changed:
The HMI focus varies by about -0.4 focus steps/Degree celcius. See plot and email below for more details:
A l l ,
I h a v e a t t a c h e d a n u p d a t e d o f t h e f o c u s v e r s u s t i m e . F i r s t p a g e s h o w s t h e f o c u s
a s a f u n c t i o n o f F S N f o r t h e t i m e s s i n c e d o o r o p e n i n g . V e r t i c a l d o t t e d l i n e s h o w
t h e t i m e o f t h e + 7 C t e m p e r a t u r e c h a n g e . D i a m o n d s a r e f o r t h e f r o n t c a m e r a ,
s q u a r e s f o r t h e s i d e . A s y o u c a n s e e t h e f o c u s c h a n g e s b y a b o u t - 0 . 4 s t e p s / C .
S e c o n d p a g e s h o w s t h e f o c u s a s a f u n c t i o n o f t i m e ( r o u g h l y ) s i n c e t h e
t e m p e r a t u r e c h a n g e . T h e l a s t 1 1 d e n s e l y s p a c e p o i n t s a r e t h e o n e s w e t o o k o v e r
t h e l a s t 2 4 h o u r s s p a c e d b y 2 . 4 h o u r s . A s y o u c a n s e e t h e c h a n g e s a r e
e x c e e d i n g l y s m a l l .
T h e s e c o n d p l o t s h o w s t h e t e l e s c o p e t e m p e r a t u r e s o v e r t h e l a s t 4 8 h o u r s . A s y o u
c a n s e e t h e r e i s a p e a k t o p e a k a m p l i t u d e o f a b o u t 0 . 4 C o r 0 . 5 C . S c a l i n g t h a t
n u m b e r b y - 0 . 4 s t e p s / C w o u l d h a v e g i v e n a b o u t 0 . 2 s t e p s o f v a r i a t i o n . T h e r e a s o n
t h a t y o u s e e l e s s i s l i k e l y t h a t i t i s a b u l k t e m p e r a t u r e c h a n g e r a t h e r t h a n a
c h a n g e o f t h e r i m o n l y .
A l l i n a l l t h i n g s l o o k g o o d a n d t h e r e i s p r o b a b l y l i t t l e n e e d f o r f r e q u e n t f o c u s
s w e e p s .
