OL 16A/ 65A/ 83A Programmable DC Current Sources0 pages

Ulletin 121 / Rev. 4-03
OL 16A, 65A, and 83A
Programmable DC Current Sources
The OL 16A, 65A and 83A are microprocessor controlled,
precision DC current sources specifically designed to
accurately operate tungsten filament lamp standards and
calibration sources. The power output range is 10 to 100
watts for the OL 16A, 10 to 200 watts for the OL 65A and
10 to 1000 watts for the OL 83A. All three units feature:
- Output current accuracy of ±0.01% or better
- Controlled ramp up / ramp down of the lamp current
- Simultaneous digital readout of lamp current, voltage,
and power
- Ability to set lamp current, voltage, or power
- Lamp "library" for storing and recalling the operating
parameters & description for up to 10 different lamps.
The user-defined operating parameters include lamp
current, voltage or power, current limit, calibration due
interval & lamp hours. A separate elapsed time meter
keeps track of the lamp hours for each of the 10 lamps.
A calibration due warning message will appear upon
power up when the lamp hour’s limit is exceeded and/or
1 year has elapsed since last calibration.
- RS-232 (standard) and IEEE-488 (optional) computer
interface
Tungsten lamp standards must be operated at their
specified calibration current in order to realize the
accuracy of the standard. A small error in setting the
lamp current can induce a sizeable, wavelength
dependent error in the spectral output of the lamp. The
OL 16A/65A/83A enables the lamp current to be set to
an accuracy of better than ±0.01%, a factor of about 25
better than most other commercial power supplies,
which are typically 0.25%. The advantage of the OL
16A/65A/83A's increased accuracy is illustrated in the
table below.
SPECTRAL IRRADIANCE UNCERTAINTY
Due To
ERROR IN SETTING LAMP CURRENT
Wavelength
(nm)
OL 16A/65A/83A
± 0.01%
Other Supplies
± 0.25%
250 0.12% 3.0%
300 0.09% 2.3%
550 0.04% 1.0%
1000 0.02% 0.5%
2000 0.01% 0.3%
*Tungsten Lamp @ ~3000K
In order to eliminate electrical shocking of the lamp due to
high initial current surges, a ramp function is used to
control the turn-on current rise. Once the instrument is
turned on, the current automatically increases at a slow,
safe rate until the set current is reached. A fail-safe, shut
down circuit protects the lamp standard against any
equipment malfunctions.
The OL current sources will maintain their accuracies
while experiencing ±10% fluctuations in line voltage and
±10% variance on the load voltage. These features
effectively compensate for transients in the power line and
variations in resistance from one lamp to another. The
power supplies are packaged in a chassis suitable for
mounting in a 19" cabinet rack.