User Manual

Page 74
ELR 9000 Series
www.elektroautomatik.de
[e-mail]
EA Elektro-Automatik GmbH
Helmholtzstr. 31-33 • 41747 Viersen
Germany
Fon: +49 2162 / 3785-0
Fax: +49 2162 / 16230
4.4 Calibration
4.4.1 Preamble
The devices of series ELR 9000 feature a calibration function that is intended to re-calibrate a few major parameters
once the move out of tolerance. This is limited to compensate small differences of up to 1% or 2%, but not more.
There are several reasons which could make it necessary to re-calibrate a unit: component aging, component
deterioration, extreme ambient conditions, high frequent use
In order to determine whether a parameter is out of tolerance, the parameter must be veried rst with measurement
tools of high quality and at least half the error tolerance than the one 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 calibrate the input current of model ELR 9080-510, which is 510A
max. and given 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 and it also 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 measurement and re-calibration, a few tools and certain ambient conditions are required:
• A measurement device (multimeter) for voltage, with a max. error of half the ELR device’s voltage error in the
voltage range where it has to measure the input voltage. That measurement device can also be used to measure
the shunt voltage when calibrating the current
• If the current is also going to be calibrated: a suitable DC current shunt, specied 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
• Warmed up ELR unit, which has been run for, like, 10 minutes under 50% power
• A voltage / current source which is capable of providing at least 102% of the max. voltage and current of the ELR
device, or separate voltage source and current source units
Before you can start calibrating, a few measures have to be taken:
• Let the ELR device warm up in connection with the voltage / current source
• Remove remote sense connection, if connected
• Leave remote control, deactivate master-slave mode, set device to U/I mode
• Install the shunt between source and ELR device and make sure it is cooled somehow, for example when plac-
ing 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 external measurement device to the DC input or to the shunt, depending on whether the volltage is
going to be calibrated rst or the current
4.4.3 Calibration procedure
After the preparation, the device is ready to be calibrated. From now, a certain sequence of parameter calibration
is important. Generally, you don’t need to calibrate all four parameters of voltage and current, but the actual value
of voltage (U-Monitor) is connected to the set value of voltage (U-Set), same for current. So these two connected
parameters should always be calibrated together. Important:
The set value (U or I) must always be calibrated before the related actual, i.e. monitor value
and also as precise as possible.
The calibration procedure, as explained below, uses an example of the model ELR 9080-170. Other models are
treated the same way, with values according to the ELR model and the required source.