Conversion mode
The so-called conversion mode determines the speed and latency of the analog measurement in the EL3356. The characteristics:
Mode | Meaning | typ. latency | EL3356 | EL3356-0010, EL3356-0090 | typ. current consumption |
|---|---|---|---|---|---|
0 | High precision Analog conversion at 10.5 kSps (samples per second) Slow conversion and thus high accuracy | 7.2 ms | x | x | 70% (see Technical data regarding nominal value) |
1 | High speed / low latency Analog conversion at 105.5 kSps (samples per second) Fast conversion with low latency | 0.72 ms | - | x | 100% (see Technical data regarding nominal value) |
Due to the conversion principle of the EL3356, the analog voltage is only available as a digital value after a defined time. This is shown in Fig. Latency of the analog/digital converter.
A step signal 0->1 is applied to the input. The measured value is reached and readable within the defined accuracy after 7.2 or 0.72 ms, depending on the conversion mode 0/1. At this time the timestamp is also acquired in Distributed Clocks mode. In real operation a step signal is not normally connected, but rather a higher frequency but constant signal. The EL3356 then maps the input signal with the corresponding latency for further processing, for which reason faster querying of the sampling unit at shorter intervals than the latency (EL3356-0010 allows up to 100 µs and EL3356-0090 allows up to 150 µs) makes sense for true-to-detail mapping of the analog input signal.
It is not possible to change the specified latency.
Beyond that the following are individually adjustable in each mode via CoE
- activation of the averager
- activation of the filter
- type of filter
The EL3356 has only mode 0, the El3356-0010 and the EL3356-0090 have modes 0 & 1.
Mode change (EL3356-0010, EL3356-0090 only)
In particular for dynamic weighing procedures it may make sense to considerably change the measuring characteristic during the weighing procedure. For example, if a bulk material is filled by the sack within 5 seconds, a very open filter should initially be used so that the measured value quickly follows the fill level. During this phase it is of no importance that the measured value is very inaccurate and subject to high fluctuations. If the sack is >90% full, filling must be slowed down and the loading must be followed with higher accuracy; the filter must be closed. Therefore the two conversion modes can be switched via the process data bit “Sample mode“ in the EL3356-0010 and EL3356-0090 in relation to the processing of the analog values.
The mode change takes about 30 ms, during which time the measured values are invalid and indicate this by the status byte.
