Download 1 - NSCA TRA-CAL

Operating instructions-7A42
TABLE 2-3 (CONT)
7A42 Operator Message Summary
Code
Mnemonic
THRESH R E 0
+I NO F U N C A
13
Description and Corrective Action
1
I
NO FUNC B
Either a LEVEL key or the PROBE OFFSET key was
pressed without pressing the THRESH key first.
The THRESH key must be lit to change a threshold
level or acquire a probe offset.
The A THEN B key was pressed without having
programmed function A; or while in A THEN I3 mode
function A was CLEARed. Both trigger functions
(A and B) must be programmed for proper A THEN B
operation. Program function A; then proceed.
The A THEN B button was pressed without having
programmed function B; or while in A THEN B mode
function B was CLEARed. Both trigger functions
(A and B) must be programmed for proper A THEN B
operation. Program function B; then continue.
WARNING BEEPS: Although no messages are displayed, short warning beeps are
issued to indicate "out of range." A beep will sound when the
VOLTS/DIV keys are pushed beyond the availableselectionsor
when the variable threshold level reaches its limits.
NOTE
The audible beep can be turned off; refer qualified Service Personnel
to the 7A42 Service Manual (Volume 1).
SIGNAL CONNECTIONS
Generally, probes offer the most convenient means of connecting input signals to
the instrument. They are shielded to prevent electromagnetic interference. The
10X probe offers a high input impedance to minimize circuit loading when
measurements are made; signal amplitude is attenuated by a factor of 10 by the
probe, so the scale-factor readout is switched to indicate the correct scale factor.
The limited TTL/ECL VOLTS/DIV ranges require that attenuation be used to
obtain useful signal levels at the 7A42 channel inputs. Ten times probes are
recommended on the channel inputs to attenuate TTL and ECL signals; otherwise
10X attenuators should be used. When 10X probes are used the VOLTS/DIV and
SWITCHING THRESHOLD are automatically compensated to reflect the
characteristics at the probe tip.