C A L I B R A T I O N A N D T R O U B L E S H O O T I N G
Remote Calibration of the LDX-32420 Current Source
80
LDX-32420
C H A P T E R
6
I
PD
Current Calibration
The following procedure is for calibration the LASER I
PD
constant current source.
This procedure calibrates the feedback circuits for constant I
PD
and constant P
PD
modes. When these values are reached and are stable, the user enters the actual
value of the current, as measured by an external DMM. The LDX-32420 Current
Source then automatically calibrates the current measurement circuits.
Configure the current source in the following manner for the I
PD
current
calibration:
* For this calibration, it is recommended that the current from the LDX-32420 only passes the primary of the current transducer
once.
a.
With the LASER output off, connect the secondary of the current transducer such
that is first passes through the ammeter portion of the DMM and then into the PD
anode. Connect PD cathode to transducer common. The DMM will now be able to
directly measure PD current.
b.
Enter the
LAS:OUT ON
command to turn the LASER output on. Verify proper
operation, i.e. the IPD output should be close to the setpoint, and the unit should not
be in current limit (read the limit status via the
LAS:COND?
query, bit 0).
c.
Enter the
LAS:CAL:MDI
command to place the Current Source in its I
PD
Current
Calibration mode. The Current Source will increase the laser current output until the
current at the PD monitor (I
PD
) inputs equals the targeted setpoint.
d.
After a few seconds, the Current Source will be ready for the actual I
PD
current to be
entered via the
LAS:MDI <nrf value>
command. The measured value of the
current should not be entered until the Current Source is ready to receive it. The
Current Source will be ready to receive the current value when, after a
LAS:CAL:MDI?
query is sent, the response from the Current Source is "1".
e.
Once the actual I
PD
value is entered via the
LAS:MDI <nrf value>
command, the
Current Source will store the new calibration value. It will then set the output to
approximately one-fourth (1/4) of the original current. (For example, if the first
calibration setpoint was 4000 µA, the second setpoint will be 1000 µA.) Then, it will
be ready to receive the second calibration value.
f.
Input the second actual (measured) monitor diode current (as an
<nrf value>
) as
in Step d.
g.
Once the second actual IPD value is entered via the
LAS:MDI
command, the new
calibration constants will be calculated and stored into non-volatile memory. The
OPC?
query may be used (after the
LAS:MDI
value is sent) to determine when the
calibration is completed. Or, wait about two seconds before continuing with other
GPIB commands.
Function
State
COMMAND
LASER MODE
P (constant power)
LAS:MODE:MDP
RANGE
Low (lowest per instrument model)
LAS:RAN LOW
LIMIT
90% of FS (full scale of range)
LAS:LIM:ILOW
I
PD
SETPOINT *
80% of FS
LAS:MDI
Summary of Contents for LDX-32420
Page 3: ......
Page 9: ...L I S T O F FIG U R E S vi LDX 32420...
Page 11: ...L I S T O F TA B L E S viii LDX 32420...
Page 17: ...WA R R A N T Y xiv LDX 32420...
Page 41: ...O P E R A T I O N Operating a Laser in Constant Power P Mode 24 LDX 32420 C H A P T E R 2...
Page 57: ...RE M O T E O PE R A T I ON Error Messages 40 LDX 32420 C H A P T E R 3...
Page 103: ...C A L IB R A TI O N A N D TR OU BL E S HO O T IN G Error Messages 86 LDX 32420 C H A P T E R 6...
