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ELR 9000 Series
4.4
Calibration
4.4.1 Preface
The devices of series ELR 9000 feature a function to re-adjust the most important input values when doing a
calibration and in case these values have moved out of tolerance. The re-adjustment is limited to compensate
small differences of up to 1% or 2% of the max. value. There are several reasons which could make it necessary
to re-adjust a unit: component aging, component deterioration, extreme ambient conditions, high frequent use.
In order to determine if a value is out of tolerance, the parameter must be verified first with measurement tools of
high accuracy and with at least half the error of the ELR device. Only then a comparison between values displayed
on the ELR device and true DC input values is possible.
For example, if you want to verify and possibly re-adjust the input current of model ELR 9080-510 which has 510
A maximum current, stated with a max. error of 0.4%, you can only do that by using a high current shunt with max.
0.2% error or less. Also, when measuring such high currents, it is recommended to keep the process short, in order
to avoid the shunt heating up too much. It is furthermore recommended to use a shunt with at least 25% reserve.
When measuring the current with a shunt, the measurement error of the multimeter on the shunt adds to the error
of the shunt and the sum of both must not exceed the given max. 0.4% of the device.
4.4.2 Preparation
For a successful calibration and re-adjustment, a few tools and certain ambient conditions are required:
•
A measurement device (multimeter) for voltage, with a max. error of half the ELR’s voltage error. That measure-
ment device can also be used to measure the shunt voltage when re-adjusting the current
•
If the current is also going to be calibrated: a suitable DC current shunt, ideally specified for at least 1.25 times
the max. input current of the ELR and with a max. error that is half or less than the max. current error of the ELR
device
•
Normal ambient temperature of approx. 20-25 °C
•
An adjustable voltage & current source which is capable of providing at least 102% of the max. voltage and cur-
rent of the ELR device, or separate voltage source and current source units
Before starting the calibration procedure, a few measures have to be taken:
•
Let the ELR device warm up for at least 10 minutes under 50% power, in connection with the voltage / current
source
•
In case the remote sensing input is going to be calibrated, prepare a cable for the remote sensing connector to
DC input, but leave it yet unconnected
•
Abort any form of remote control, deactivate master-slave mode, set device to
U/I
mode
•
Install the shunt between source and ELR device and make sure the shunt is cooled somehow. For example ,
you might want to place it in the warm air stream coming out of the rear of the ELR device. This helps the shunt
to warm up as well to operation temperature
•
Connect suitable measurement devices to the DC input and to the shunt, depending on whether the voltage is
going to be calibrated first or the current
4.4.3 Calibration procedure
After the preparation, the device is ready to be calibrated. From now on, a certain sequence of parameter calibra-
tion is important. Generally, you don’t need to calibrate all three parameters, but it is recommended to do so.
Important:
The input current calibration should be done before any voltage calibration, because the cali-
brated input current is used for voltage calibration.
When calibrating the input voltage, the remote input sense on the rear of the device has to be
disconnected.
The calibration procedure, as explained below, is an example with model ELR 9080-170. Other models are treated
the same way, with values according to the particular ELR model and the required power source.
