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Overrange Indications The digitizer indicates an overrange condition (input greater than the
selected range can measure) by returning the values shown in Table 3-3.
An amplifier overrange (single-ended or differential input) sets bit 0 in the
digitizer’s Questionable Signal Status Register. However, the overrange
does not generate an error message.
Retrieving Readings Each time the digitizer is INITiated it takes a new set of readings. Readings
are retrieved directly from the A/D converters or from digitizer memory
(Figure 3-11). Each new set of readings overwrites any readings currently in
memory. Retrieved readings are transferred over the VME (VXI data
transfer) bus or over the Local bus. The methods used to retrieve readings
are listed below, relative to their transfer rates.
• READ? (page 139) slowest
• FETCh? (page 139)
• DIAGnostic:UPLoad:SADDress? (page 141)
• VME bus Data register access(page 146)
• Local bus transfers (page 156) fastest
These methods are described in the following paragraphs. Table 3-4
summarizes the digitizer’s data transfer modes and transfer rates.
Condition Reading A/D Code
A/D Overrange
(positive reading)
+9.900000E+037 +2047
A/D Overrange
(negative reading)
-9.900000E+037 -2046
*S/E Input Amplifier
Overrange
or
Differential Input
Amplifier Overrange
-9.900000E+037 -2048
*A single-ended input amplifier overrange occurs when the input
signal exceeds
± 5V.
A differential input amplifier overrange occurs on the 0.1V, 0.2V, 0.5V,
1V, 2V, and 5V ranges when the signal on the HI or LO input exceeds
±11V. An overrange occurs on the 10V, 20V, 50V, and 100V ranges
when the signal on the HI or LO input exceeds
±110V.
Table 3-3. Digitizer Overload Readings
Chapter 3 Understandin
g
the HP E1429 Di
g
itizer 137