Philips 6652C - Mathematics; Trigger Settings

TRIGGER SETTINGS
The PM 6652/54 offers a variety of trigger pos-
sibilities, such as trigger slope, input impe-
dance, AC/DC coupling and two trigger level ran-
ges -5 ••• +5V and -50 ••• +50V.
As further described in the chapter "Measurement
Theory", always try to set the controls to AC
coupling and x10 attenuation for frequency mea-
surements and DC coupling with no attenuation
for time measurements.
for many measurements it is vital to have a
good impedance matching to avoid reflections
which might make the trigger level setting very
difficult. Always use the 50 Ohm termination in
50 Ohm systems.
,-TRIGGER LEVEL--,
SLOPE
OV 0 READ 0 OV
~~~-~
AUTO
-SV sv
ATT SETA KEYBOARD SETB
X1 IC!JI X10
D
[!]
D
COM
CHECK
1M n IC!Jiso n
G GJ
Fig 4.~ Trigger controls.
Trigger level setting
The trigger level can be set in one of three
ways: Auto, keyboard or potentiometers.
In AUTO mode the counter automatically calcu-
lates and sets the triggering to the 50%
level of the input signal, or for rise/fall
time measurements at 10% and 90% of the sig-
nal's amplitude. AUTO is automatically selec-
ted immediat-ely after power on unless a pro-
gram dictates otherwise.
- When KEYBOARD is selected, the trigger levels
could be entered automatically from a stored
panel program, or manually via the keyboard.
When the trigger levels are set via keyboard
it is good practise to store the values in
one of the program positions.
- Potentiometers are selected when neither AUTO
nor KEYBOARD pushbuttons are depressed. Note
that potentiometer values cannot be stored in
a stored panel program.
When the trigger controls have been set, the
functioning of the trigger circuits can easily
be checked on the trigger indicators , one for
each channel. The LED:s show the state of the
triggering:
ON the signal is above the
trigger level.
OFF the signal is below the trigger level.
BLINKING the signal is crossing the hysteresis
band (correct triggering).
MATHEMATICS
On many occasions it is convenient to modify the
measured result before presentation in order to
make it easier understood. Some examples: An odd
result from a transducer can be changed to rpm,
or a frequency that has to be monitored may be
subtracted before displayed, and the display
will only show the deviation.
The formula: Display = K x measured value + l
is used when the DISP::K:xX+L is selected (LED
on). In the formula K and L are set by the user.
r-MATH--,
01SP=K· X+L
Gl
K=
D
L=
D
SET \11A KEYBOARD
Fig. 4. 4 Mathematical controls.
K and l are set by pressing K= and/or l=, ente-
ring the ' value on the key panel, then pressing
ENTER. Any further depression of K:: or l:: will
show the last values ent. ered, and will set the
ENTER light on. RESET will cancel the ENTER, but
will not change the previous values of K and l.
Unless stored in a stored panel program, any va-
lues set for K and L will reverty to 1 and 0 re-
spectively when power is switched to ST BY.
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