13
7
Metering
As shown in Section 5, the circuit being monitored is connected directly to the SS9007 Mini CT
Meter, providing a power supply for the device as well as enabling high accuracy voltage
measurements. Current is measured using a clip-on current transformer (CT), with nominal primary
current ratings of 40A and 120A available as standard.
Each individual Saturn South meter is calibrated in the final stage of the production process. The
calibration procedure matches each device to a particular CT variant, meaning that measurements
will not be accurate if a device calibrated for a 120A CT is used with a 40A CT. Furthermore, given
the wide range of secondary current ratings available for CTs, the SS9007 Mini CT Meter must only
be used with the supplied CT.
IMPORTANT: Attaching a third party CT to the device can damage the device and will void the
product warranty.
SS9007 Mini CT Meter devices have a ‘variant label’ on the front panel that describes the rated
primary current (and hence the CT variant to use), as well as indicating whether or not the device
has an internal relay. For example:
“
120A
” –
Device is rated for a 120A nominal primary current.
“
40A/R
” –
Device is rated for a 40A nominal primary current and includes an internal relay.
Max calibrated voltage
error
0.1%
Max calibrated current
error
0.5%
Typical absolute transfer
ratio error for 120A CT
< 0.5%
Typical absolute transfer
ratio error for 40A CT
< 0.5%
Region of linearity for
120A CT (<1% error)
8% to >110% of rated
primary current
Region of linearity for
40A CT (<1% error)
15% to >150% of rated
primary current
Figure 5: Measurement accuracy specification
For a full list of measured attributes delivered by the SS9007 Mini CT Meter, please refer to Section
8.
