General Hardware Conditions For "Extended Measurement - Siemens SINUMERIK 840C Installation Instructions Manual

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12.29.2

General hardware conditions for "Extended measurement"

"Extended measurement" G720/1 can be programmed for every measuring circuit variant:
• Standard measuring circuit with SPC 6FC5 111 0BA0.-0AA0,
• Standard measuring circuit with PCA 6FC5 111 0BA0.-0AA0,
• HMS measuring circuit 6FC5 111 0BA..-0AA0 and
• SIMODRIVE 611D modules with indirect/direct measuring channel.
The variation in hardware properties gives rise to the following boundary conditions which must
be noted when the function is programmed to avoid output of RESET alarms.
SPC(214) and HMS measuring circuit (6FX1121-4BA02, 6FX1121-4BA01):
• Only one probe input can be active, the negative signal edge is always evaluated.
"Extended measurement" G720/1 can be performed only with the first probe input, the
second probe input is ignored. (This restriction does not apply to "Inprocess
measurement" 720 with which both probes can be activated alternately, but is necessary
for the extended function to ensure an unambiguous assignment of probe inputs, even for
SIMODRIVE 611D mixed operation).
• Response to probe "bouncing":
In the case of multiple edges (probe "bouncing") within one position controller cycle, the
measured value is read from the measuring circuit belonging to the last edge.
• When programming the measuring edge, switch S4 on the CSB module must be taken into
account. Depending on switch S4, this module can invert the signal of the probe.
PCA measuring circuit (successor to SPC214, 6FX1121-4BA03):
• Only one measuring probe can be active. The PCA measuring circuit can react in the
position controller cycle to the following edge sequences: "rising/rising", "falling/falling" or
"alternately rising/falling falling/rising".
In contrast to the SPC measuring circuit, evaluation of the second probe input is supported
as an alternative for the PCA (measuring probe inputs can be switched over).
Only one measuring edge per position controller cycle can be sensed (either positive or
negative). For alternating measuring edges, therefore, the PCA measuring circuit module is
reprogrammed internally (software function) to the next probe edge in the next position
controller cycle after every new measured value is received. When "alternating measuring
edges" is programmed, the user must ensure that the measuring frequency is smaller than
the position control frequency.
• Response to probe "bouncing":
In the case of multiple edges (probe "bouncing") within one position controller cycle, the
measured value belonging to the first edge is always read out.
© Siemens AG 1992 All Rights Reserved
SINUMERIK 840C (IA)
12.29.2 General hardware conditions for "Extended measurement"
6FC5197- AA50
12 Functional Descriptions
12–301