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The four fields of the data string are: 1. Header, 2.
Numerical Data Field, 3. GOOD/BAD Indicator, and 4.
End Terminator. Each field has the same number of
characters for all test functions, allowing the same
subroutines to process any returned data. Here are the
details for each field of data.
Header:
The first three characters identify the test
function which produced the reading. The three
characters sent back from the instrument are usually the
same as the test function commands used to select a
function when the LC103 acts as a listener. These codes
let the software identify the source of the data, confirm
that the correct function is producing readings, or label
the data for future retrieval.
In certain cases, the Header identifies some special
conditions, such as errors or shorted or open
components. The computer software should test for these
conditions before processing readings for accurate test
results, as explained in the section Error Testing below.
Numerical Data Field:
The 11 spaces following the
Header (characters 4 through 14) contain the numerical
results of a talker function. The values returned from a
test function are in scientific notation, allowing any
value to be represented with the same number of
characters. Error codes appear as a single digit (from 1
to 7) without the scientific notation.
GOOD/BAD Indicator:
The single space following the
Numerical Data Field (the fifteenth character) is reserved
for the results of the automatic LC103 GOOD/BAD
tests. The single letter “G”, “B”, or “R” appears in this
position when the LC103 has sufficient information to
determine if the reading is good or bad or if the
component needs to be removed from the circuit. If a
piece of data (such as the tolerance or ideal value) is
missing, the position occupied by the GOOD/BAD
Indicator is left blank.
NOTE: A leakage test function may require from 4 to 8
readings for the leakage to settle before providing a
GOOD/BAD indication.
End Terminator:
All data ends with both a carriage
return (ASCII decimal 13) and a linefeed (ASCII
decimal 10) character. Many programs respond to either
character, while others only respond if the linefeed is
present. A few programs, however, may stop accepting
data when the carriage-return character is sent, leaving
the LC103 hung up waiting to send its last (linefeed)
character. If this happens, you may need to put an extra
GET or INPUT statement into your program to let the
LC103 send its last character into an unused variable.
Error Testing
Your computer software should test for error conditions
(often called “error trapping”) after every reading has
been collected from the LC103 to avoid an error from
causing unexpected results. The software can either
report the error or skip over it, but should do one or the
other without crashing the program. If your program is
particularly advanced, it may test for the type of error (as
indicated by the error number returned in the Numerical
Data Field) and then branch to different parts of the
program which can take the correct action to compensate
for the error.
Error
Description
1
Component Type selection error
2
Entered value beyond range of unit
3
Entered value beyond range of test
4
Value beyond zeroing limit
5
No voltage entered
6
Invalid RS232 command
7
Component out of test range
8
Entered string is too long
Table 10 - Error codes returned by the LC103 during
RS-232 operation.
Most errors cause the LC103 to return a Header with the
three letters “ERR.” A simple test for this Header
allows the program to be alerted to the error. The value
of the Numerical Data Field tells the computer which of
eight errors have occurred. The error codes are
summarized in Table 10. Refer to the section entitled
“Error Messages” for a more detailed explanation of
each error condition.
Shorted Capacitors
The LC103 automatically senses if a capacitor is shorted
before performing a capacitor value test. If a short is
detected, the LC103 sends the letters “SHT” as the
Header Field of the returned data and displays “SHORT”
in the display. Adding one line of program code will test
for this condition. This line should appear before any
part of the software program which depends on a value
reading, so that the value test will be skipped in case of a
shorted capacitor.
Open Inductors
The LC103 automatically senses if an inductor is open
(or if the test leads are not connected to the coil) before
performing an inductor value test. If an open is detected,
the LC103 sends the letters “OPN” as the Header and
displays “OPEN” in the display. One additional program
line will test for this condition. Place this line before any
portion of the program which depends on an inductor
value reading, so that the value test will be skipped in
case of an open inductor.
