ABB SA/S 12.16.6.1 Product Manual - Knx Device
ABB i-bus
®
KNX Device
technology
38 2CDC 505 056 D0207 | SA/S
For a non-sinusoidal curve type, values result that can greatly diverge from
the real RMS value. This measurement method is used in most commercially
available analogue and digital multimeters that are calibrated for sinusoidal
curve types.
In this case, a true RMS meter or a “non-true RMS meter” are frequently
referred to, e.g. METRAHit 13S.
Note
With non-sinusoidal currents, there are considerable differences between
a high-quality true RMS meter and the displayed values of the SA/S. For
this reason, a meter should be used for comparative measurements that is
also calibrated for sinusoidal AC currents.
Only currents exceeding 20 mA can be displayed for technical reasons.
Interference is suppressed by an RC element, and the displayed value is
stabilised. The RC element has a time constant
τ of about 300 ms.
The current values are scanned cyclically every 320 ms. Thus a change in
the current can be safely detected every 320 ms and sent on the bus if
required.
The almost exact value is displayed after 5
τ ≈ 1.5 s.
The following technical specifications apply for current detection:
Detection range:
0.02…20 A
Accuracy:
+/- 2 % of actual current value +/- 20 mA
Time constant:
300 ms
Scanning frequency:
320 ms
Load current I
Load
AC:
0…20 A, sinusoidal
I
Load
DC:
Is not detected
Frequency range:
45…65 Hz
Ambient temperature :
-5 °C…+40 °C
Examples:
Detected current value
Max. inaccuracy
300 mA
+/- 26 mA
2 A
+/- 60 mA
16 A
+/- 340 mA
20 A
+/- 420 mA
For every output, the determined current values can be represented via a 2
byte or 4 byte value output object. The currents are represented in mA as
counter values (2 byte, DTP 7.012) or as floating values (4 byte, DTP
14.019).