HP 5890 SERIES II Service Manual page 17

To leave this mode of testing, press any of the instrument function keys.
Calib and Test (Clear Dot 8) Set PID Controls
Calib and Test (Clear Dot 9) Disp Temp & Demand
Test Chromatogram Signal Output Test
This diagnostic test is selected from the keyboard by pressing One of the signal selection keys either
SIG 1 or SIG 2 and the 9 key on the numeric key pad and the ENTER key. Test plot mode is confirmed
by the display showing SIGNAL 1 (or 2) TEST PLOT. Pressing SIG 1 (or 2) a second time displays
the current signal level value (which is 0.0 initially). This permits monitoring the output signal.
The test chromatogram, which is permanently stored in the HP 5890 SERIES II, is initiated by pressing
the START key. Each chromatographic cycle consists of three peaks. Each peak is about 1/10 the
height of the previous peak, with the first (tallest) peak having a height value of about 125 mV at = 0
(+1 V analog output); halfheight width of this peak is about 0.13 minutes. Each cycle is about 1.5 min-
utes in length. The chromatogram will continue to cycle until the STOP key is pressed. The test chroma-
togram is useful as a troubleshooting aid in deciding whether a lost or noisy signal observed at a con-
nected integrating or chart recording device is due to a chromatographic problem (lost sample due to
leaks, noise due to a dirty detector, etc.), versus problems either with the integrating/recording device
itself, or in its connecting cables.
If the test chromatogram does not exhibit any problems at the integrating/recording device, a chromato-
graphic problem is likely to exist; if the test chromatogram exhibits noise, or does not appear at all, the
problem is most likely to be hardware related. Check setpoints on both the HP 5890 SERIES II and the
integrating/recording device.
SVC 1- 10
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