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•
Source selection (maximum 6 sources): Specify here which channel, or which
source and value (Type: Minimum, Maximum or Instantaneous value) is to be sent.
The maximum or minimum value of the source signal is the relevant value since the
last sampling time. This detects extreme values that occur between samples (Sam-
pling interval).
In the Precision field you define the number of digits in the measured value. You
should make the number only as large as necessary, so as to keep the packet
length, and thus the computing and transfer time, short. The actual length of the
measured value may vary in individual cases however.
•
Error value: An invalid measured value is replaced by this value. You can only detect
the invalidity of a value by this. No validity flags or the like are transmitted.
•
Values per packet (displayed only): Shows the number of measured values in an
Ethernet packet. This value should tend to be less than 750. Each packet remains in
a buffer until being successful transferred (via TCP). If the connection is bad, there
may be a shortage of space, so packets may be lost. To reduce the packet size, you
can
•
shorten the send interval, or
•
extend the sampling interval, or
•
reduce the number of channels (sources) to be transmitted.
•
HTTP response (displayed only): The response from the http server according to
RFC 2616 (https://tools.ietf.org/html/rfc2616). Values from 200 to 299 indicate a
successful transfer; all other values indicate an error. But you must run diagnostics
at network level.
•
Info (displayed only): Shows the status of the firmware, e.g. waiting for IP address,
creating socket, connecting or connected.
Error handling
The PPMP packets are transmitted via sockets and TCP/IP stacks, and processed at the
receiver by an HTTP server. These PPMP data receivers behave differently depending on
their manufacturer and configuration. The data receiver also does not send a response
according to the protocol. However, the PPMP expression (json) is enclosed in an http
frame. The http protocol stack of the receiver is usually the default stack under Win-
dows or Linux, and sends a response - ideally 200. The ClipX can therefore only detect
transmission errors in this way, and the System LED lights up yellow. If there is also an
error code, this indicates that there is at least one connection to the PPMP receiver.
If the socket tells the ClipX that three packets in a row could not be sent, the socket is
closed and the connection is restarted. The connection is also restarted if no response
116
Operation via Ethernet/OPC UA/PPMP
ClipX
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