Sampling Speed with Irinos

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Sampling Speed with Irinos

For all Irinos systems, the real-time capability is independent of the number of probes (measurement channels), since each Irinos box has its own measurement value buffer. With the

Irinos IR, most boxes are able to acquire 20000 samples/s, and with the

Irinos EC, most boxes are able to acquire 4000 samples/s.

 

Two quick rules of thumb for 99% of applications are:

If you limit the sampling speed to 1000 samples/s, there is no need to think about any details. Or:

If you limit the sampling speed to 10000 samples/s and if you have a maximum of 4 Boxes, there is no need to think about any details.
(With the Irinos EC, the max. speed still is 4000 samples/s.)

 

 

The sampling period used with the NMX DLL must be an integer multiple of the minimum sampling period of the system. The following table lists typical sampling speeds:

Sampling Speed

[samples/s]

Sampling Period

Irinos IR

Irinos EC

20.000

50 µs

OK

not supported

10.000

100 µs

OK

not supported

6.666

150 µs

OK

not supported

5.000

200 µs

OK

not supported

4.000

500 µs

OK

OK

2.000

500 µs

OK

OK

1.000

1000 µs = 1 ms

OK

OK

500

2000 µs = 2 ms

OK

OK

200

5000 µs = 5 ms

OK

OK

100

10000 µs = 10 ms

OK

OK

 

 

The memory is dimensioned so that the measured values can be buffered for at least 10 seconds at the maximum sampling rate. If the sampling rate is lower, this time increases accordingly.

Only the transmission time to the PC depends on the number of channels and the measuring rate. Since the data transmission to the PC and the PC itself do not have realtime capabilities, no guaranteed transmission time can be guaranteed. However, typically a transmission rate can be achieved, which is almost constant and thus close to realtime.

For time-limited real-time measurement, the transmission rate is relevant for calculating the typical time between "start of sampling" and "all measurement data available on the PC". This time is called "transfer time".

For endless measurement, the transmission rate is relevant for determining the maximum possible sampling speed.

 

Typically achievable transmission rates are listed in the following table:

Irinos System

Typical transmission rate RTR-32 with 32 Bit measurement channels,

e.g. Incremental probes

Typical transmission rate RTR-16 with 16 Bit measurement channels

e.g. Inductive probes

Irinos IR

approx. 200.000 values/s

approx. 400.000 values/s

Irinos EC

approx. 80.000 values/s

approx. 160.000 values/s

As shown in the table, the transmission rate also depends on the native data type(s) of the measurement channels used. If mixed types of measurement channels are used, then the typical transmission rate will be in between the given values.

 

Some examples are provided here to give a quick guidance. For a detailed examination, calculation formulas are given below.

Examples for Transfer Time for a time-limited sampling with a duration (Start -> Stop) of 10 seconds:

Configuration

Irinos IR

Irinos EC

32 Inductive Probes
(16 Bit)

10000 samples/s:

10s + 0s = 10s

-> Similar to realtime

4000 samples/s:

10s + 0s = 10s

-> Similar to realtime

32 Incremental Probes
(32 Bit)

10000 samples/s:

10s + 6s = 16s

-> approximately 6 seconds after stop, the transfer is finished

4000 samples/s:

16s + 6s = 16s

-> approximately 6 seconds after stop, the transfer is finished

32 Inductive Probes (16 Bit) + 4 Incremental Probes (32 Bit)

10000 samples/s:

10s + 0s = 10s

-> Similar to realtime

4000 samples/s:

10s + 0s = 10s

-> Similar to realtime

16 Inductive Probes (16 Bit) + 16 Incremental Probes (32 Bit)

10000 samples/s:

10s + 2s = 12s

-> approximately 2 seconds after stop, the transfer is finished

4000 samples/s:

10s + 2s = 12s

-> approximately 2 seconds after stop, the transfer is finished

 

Examples for maximum sampling speed for endless sampling:

Configuration

Irinos IR

Irinos EC

32 Inductive Probes
(16 Bit)

Theoretical maximum: 12500 samples/s

Next possible value: 10000 samples/s

Recommended: ≤ 6666 samples/s

Theoretical maximum: 5000 samples/s

Next possible value: 4000 samples/s

Recommended: ≤ 2000 samples/s

32 Incremental Probes
(32 Bit)

Theoretical maximum: 6250 samples/s

Next possible value: 5000 samples/s

Recommended: ≤ 4000 samples/s

Theoretical maximum: 2500 samples/s

Next possible value: 2000 samples/s

Recommended: ≤ 1000 samples/s

32 Inductive Probes (16 Bit) + 4 Incremental Probes (32 Bit)

Theoretical maximum: 10000 samples/s

Next possible value: 10000 samples/s

Recommended: ≤ 6666 samples/s

Theoretical maximum: 4000 samples/s

Next possible value: 4000 samples/s

Recommended: ≤ 2000 samples/s

16 Inductive Probes (16 Bit) + 16 Incremental Probes (32 Bit)

Theoretical maximum: 8333 samples/s

Next possible value: 6666 samples/s

Recommended: ≤ 5000 samples/s

Theoretical maximum: 3333 samples/s

Next possible value: 2000 samples/s

Recommended: ≤ 2000 samples/s

64 Inductive Probes
(16 Bit)

Theoretical maximum: 6250 samples/s

Next possible value: 5000 samples/s

Recommended: ≤ 4000 samples/s

Theoretical maximum: 2500 samples/s

Next possible value: 2000 samples/s

Recommended: ≤ 1000 samples/s

 

 

 


# Formulas

Following a few formulas are provided to get estimations. These formulas use the following variables:

Variable

Meaning

Unit

tTransfer

Transfer Time:
Time between "Start of sampling" and "All measurement data available on the PC"

s -> seconds

tSampling

Sampling Time:
Time between "Start" and "Stop" of sampling

s -> seconds

vsMax

Maximum sampling speed for endless sampling

values / s / channel

--> same as: samples / s

RTR

Typical Transmission rate, see table above.

values / s

NMCH

Number of measurement channels used

channels

NMCH-16

Number of 16 bit measurement channels used

channels

NMCH-32

Number of 32 bit measurement channels used

channels

NSamples

Total number of samples to be recorded

values / channel

 

Each formula is provided in a simplified form and in a detailed form.
The simplified form is sufficient for most applications as a quick check.
The detailed form is especially used, when very high performance is required.

Required value

Simplified

Detailed

Transfer time for time-limited sampling

(Time between "start of sampling" and "all measurement data is available at the PC")

Formula 1:

Sampling_Speed_Formula1

Note: tTransfer is always ≥ tSampling

Formula 2:

Sampling_Speed_Formula2

Note: tTransfer is always ≥ tSampling

Max. sampling speed for endless sampling

Formula 3:

Sampling_Speed_Formula3

Formula 4:

Sampling_Speed_Formula4

 

Example for Formula 1:

In the measurement application with the Irinos IR, 21 inductive probes, 4 analogue channels and 3 incremental probes/encoders are used. The measurement has a duration of 5 seconds at 10000 samples/s.

NMCH = 21 + 4 + 3 = 28 channels

NSamples = 5s * 10000 values/s/channel = 50000 values/channel.

RTR-32 = 200000 values/s

Sampling_Speed_Formula1_Example

--> 2 seconds after stop of sampling, all data is available.

 

Example for Formula 2:

In the measurement application with the Irinos IR, 21 inductive probes, 4 analogue channels and 3 incremental probes/encoders are used. The measurement has a duration of 5 seconds at 10000 samples/s.

NMCH-16 = 21 + 4 = 25 channels

NMCH-32 = 3 channels

NSamples = 5s * 10000 values/s/channel = 50000 values/channel.

RTR-16 = 400000 values/s

Sampling_Speed_Formula2_Example

--> Since tTransfer < tSampling, all data is available immediately after stop of sampling.

 

Example for Formula 3:

In the measurement application with the Irinos EC, 11 inductive probes + 1 incremental encoder are used.

NMCH = 11 + 1 = 12 channels

RTR-32 = 80000 values/s

Sampling_Speed_Formula3_Example

--> The maximum speed of the Irinos EC, which is 4000 samples/s, can be used.

 

Example for Formula 4:

In the measurement application with the Irinos IR, 31 inductive probes + 6 incremental encoders are used.

NMCH-16 = 31 channels

NMCH-32 = 6 channels

Sampling_Speed_Formula4_Example

--> 5000 samples/s can be used as maximum sample rate.