WTC _,

JPL.USA
SIRI.USA
TMI, USA
Inst.Geo. Mdxico
NTI, Sweden
MKVI-67702
MKVI-68018
MKVI-69036
MKVI-67401
Ä 18587
HF-15744
Table 1.1: IPC Vit Participation (cont.)
TMI
TMI
TMI
TMI
Eppley
Eppley
3. Data Acquisition and Evaluation
IPC VII Part 1: Measurements and Results
Jet Propulsion Lab!, Pasadena
Solar Energy Res. Inst., Golden
Technical Meas. Inc., La Canada_
Univ. NaL Aut. Mexico, Mexico
NaL festing InsL, Boras
EJLaue
C.V.WeUs
TJ..Stoffel
MlBerdahl
J.Stallkamp
A.Muhlia
LJ^iedquist
3.1 Timing
The measurements are taken in runs lasting 2-1 minutes with a basic sampling of 90s,. Voice announcements before
änd büzzer Signals during each event are used to inforrn the participant about the sequence. The timing for the
different instrument. types isasfollows:
a) Angstrom pyrheliomcters: during the first 90s the zero of the instrument is es^blished. From there on every
90s a icft or right rcading is performed, stariing with exposing the right hand Strip to the Sun. The first Teadingis
not taken into account. The following readings are combined as L-R, R-L, etc., yielding a total öf 11 irradiance
values per run.
b) PACRAD: the run Starts with shutter closed, after 60s the heater is turned pn during 30s (this was introdüced
after IPC III in order tö have a. well defined thermal Status of the instrument independentof the Operation sequence
beibr the run). At 270s the zero of the thermopile is read and the heater switched on again. At 360s the heatcr
voltage, current and thermopile is read, the heater tumed off and the shutter opened; From 450s on every 90s
readings are taken änd after the last one the shutter is clösed yielding 8 irradiance yalues during a tun;
c) HF type pyrheliometers: the run Starts with the shuttcr'closed, after 90s the zero i$ read. Then the heater is
turned on until 90s and then the voltage, current and thermopile is read, the heater tumed off and the shutter opened.'
From 270s onward the in$tm^
d) TMI type pyrheliometers: the run Starts with shutter closed and.the calibration procedure is performed until the
end of the first 90s. Starting at. 180s readings are taken every 90$ yielding a total öf 12 irradiance yalues during a
, run. - .. . * - '
c) Active cavity type pyrheliometers : the run Starts with a reference phase (shutter closed) during the first 90s,
foiiowed by a measuring phase (shutter open) for the next 90s. This is repeated for the next 18 minutes. A total pf
6 open and 7 closed readings are taken yielding a total öf 6 irradiance välues during a run. PM02, as the working
reference, is read at twice the pace, yielding 13 irradiances for each run. The reference phase lasts 38s and the
measuring phase 52s.
f) Other instruments: the NIP ahd PCC3-005 pyrheliometer take 12 irradiance values every 90s after a zero
rcading during the first 90s. < . . '
3.2. Acquisition
The analog data-acquisition system is based on 8 parallel DVM HP3478A with scanners and is used for the WSG
Instruments, the radiorneters of PMOD/WRC and the auxiliary data. For the input of data from thepartieipants micro-.
terminals, Burr-Brown type TM27 and TM2700 are used. The whole System is controlled by a HP Computer Series
9200, which also Stores and evaluates the data. The terminals are identified by an ünique address (terminal number)
and the input from the partieipahts cönsists of up to 8 digits foiiowed by a label A to F; indicatihg the type of data.
A maximum Of three different values ean be assigned to Ohe instrument. Thus two users can share a terminal.
3.3. Data Evaluation ;
For each instrument the irradiance and ratio to PM02 is obtained with the corresponding evaluation procedure.
After each run, a summary of measured yalues and eyäluated irradiances is printed and distributed for checking by
the parüeipants and; if necessary, the raw data can be edited for gross errors. Updated summaries with the mean