BRONKHORST®
Page 8
EL-FLOW
Base
Series Mass Flow Controllers
9.17.061
1.6.4 Calibration
EL-FLOW
Base
instruments are Air or N2 calibrated. Bronkhorst® certifies that all instruments meet the
rated accuracy. They have been calibrated using measurement standards traceable to the standards of
the Dutch Metrology Institute (VSL).
The calibration is converted to the customer’s gas and conditions using a detailed conversion model.
This conversion adds a level of calibration uncertainty.
Thumb rule for calculating the conversion uncertainty is typical:
Uncertainty < 2% x CF
for CF > 1
Uncertainty < 2% / CF
for CF < 1
With CF defined as the approximate conversion factor, which can be calculated with:
2
1
2
1
p
p
C
C
CF
in which:
n
p
C
specific heat
n
density at normal conditions
(1)
calibration fluid (Air or N2)
(2)
customer fluid
Check FLUIDAT® on http://www.fluidat.com
FLUIDAT® is a collection of routines to calculate physical properties of gases and liquids. These routines
are made available at the FLUIDAT® on the Net website.
EL-FLOW
Base
instruments are standard delivered without calibration certificate. Calibration certificates
can be ordered together with the instruments. Contact your local sales representative for more
information.
1.6.5 Features
Each instrument consists of an Analog interface, a digital RS-232 interface and a digital ModBus/RS485
interface. The analog and the digital interface can be used together at the same time.
According to the pin-designation both RS232 and Modbus/RS485 are assigned to the same pins. When
connecting these pins to either of the two, the instrument will automatically detect which protocol to
use.
Digital operation adds a lot of extra features (compared to analog operation) to the instruments.
Such as:
setpoint slope (ramp function on setpoint for smooth control)
direct reading at readout/control module or host computer
several control/setpoint modes (e.g. purge/close valve)
identification (serial number, model number, device type, user tag)
adjustable controller settings for custom controller response
