LDSS focus position and temperature readout
Contents
Introduction
The
motorized LDSS focus drive sometimes fails despite repeated attempts by the operator. This intermittent
problem is likely caused by noise on the focus encoder signal. The existing sensor is also sensitive to
humidity and dust. Cleaning the sensor seems to restore operation but costs observing time.
We will replace the original focus encoder with a lower-noise system.
Focus depends on instrument temperature. An
on-instrument temperature readout was requested by site staff and we will include a temperature readout with this upgrade.
Original
focus system
A stepper motor moves the
spring-loaded LDSS camera via a lead screw
and lever arrangement. This changes the distance of the camera from the CCD. As designed (see pages 110-113 of
G. D. Shaw's thesis), the travel range is 0.768 mm (0.030
inches) with 0.000830 mm (0.000033 inches) per motor step.
A
Super Linear Variable Capacitor (SLVC) encodes the camera position,
measuring travel directly against the instrument body. The SLVC
(inside the brass cylinder with two
setscrews shown below, mounted in LDSS on a bare-metal L-bracket) produces a 0 to 10 V
signal over a 4.9 mm travel range. This voltage signal is sent through
a
cable from the instrument to the control chassis located under the
telescope platform where it is digitized to 12 bits and reported to the
operating
software. This signal has been
noisy from the beginning, as noted in Shaw's thesis. The original LDSS
focus algorithm allowed 10 iterations to land in a +/-8 micron
error band.
Since
arriving at Magellan, LDSS has had new optics and control software
installed, but the original focus drive and readout were not changed.
Upgrade
Focus encoder
We
will replace the existing SLVC with a Linear Variable Differential
Transformer (LVDT). The LVDT is a spring-loaded and sends a 4-20 ma
current loop to an
A/D
converter. Current loops can be less
susceptible to external noise than direct voltage signals and we expect
a clean signal from this transducer. This device is protected against
dust and humidity (
IP67).
The
A/D converter will be mounted near the LVDT, inside the instrument. The
converter has an Ethernet interface so data acquisition is simple; a similar scheme is used for encoding the LDSS wheels.
The benefits of the new system are:
- A lower-noise signal should reduce the frequency of noise-induced failures
- The new encoder is better protected against dust and humidty
- The Ethernet interface allows us to remove some serial protocol
conversion hardware and the signal condtioning module
Temperature sensor
LDSS focus depends strongly on
temperature. The instrument does not now have an internal temperature sensor so
the dome air temperature is used to estimate focus offsets. By
installing a temperature sensor on the instrument, a more relevant
temperature becomes available and the instrument control software can
be calibrated to estimate the correct focus value. We will
install the temperature sensor and provide a visual readout for the
observer. Automatic temperature compensating software may be
considered for the future.
New components
Positek P103 LVDT encoder
The new LDSS focus encoder is a Positek P103 LVDT (
Positek website), model P103.10EL100NRT (cost is about
USD$620,
purchase
order). The
option
codes on the part number are for 10 mm travel (10), 4-20 ma, 2-wire
signalling (E), cabling with
IP67 class gland connection with 100 cm cable length (L100), a
front
flange mount (N), spring loaded plunger (R), and a dome end on the
plunger (T).
This
LVDT operates between -40 and +125 C and is protected against dust
and water. Because an LVDT does not have load-bearing or electrical
contacting parts, there is nothing to wear out. A current loop signal is less sensitive to power supply voltage
fluctuations and systematic offsets due to cable and connector losses,
which reduces system noise. The manufacturer's
estimated mean time between failure is about 40 years. Our P103 sensor
requires 18-28 VDC to operate.
The
primary reason for choosing this sensor is that it provides directly a
4-20 ma current loop signal that varies linearly with plunger position.
No external controllers are needed so the parts count is small,
although the device itself is bulky because it contains all the
needed circuitry.
Details are in the
product
data sheet (
local copy)
and the
installation
instructions (
local
copy). There is also an
Autocad DWG file
(
PDF
version).
The
LDSS encoder has the mounting flange as shown in the upper left
drawing, and the IP67 gland connection as shown in the lower right
drawing.
Analog Devices AD592 temperature sensor
We use an Analog Devices
AD592BNZ
temperature sensor on the LDSS spectrograph camera. This precision
transducer outputs one micro
ampere for each degree K, operating between -25 and +105 C. A precision
10Kohm metal film resistor is wired in parallel to the built-in 200K
ohm shunt in the A/D converter, so the drop resistance is 9524 ohms.
The temperature in Kelvins is thus the measured voltage times 105.0.
The LDSS software does this correction and presents degrees C to the observer.
T(Celsius) = (105.0 x Voltage) - 273.15
We do
not correct for non-linearity. The typical
non-linearity error for the AD592BNZ is 0.1 C with a maximum expected of
0.25 C in the 0 to 70 C range. We want
to measure temperature changes of about 0.5 C so the advertised
repeatability and stability of 0.1 C is adequate.
EtherTRAK ET-8INS A/D converter (IP 200.28.147.70 at LCO)
We selected an EtherTRAK model ET-8INS (
local copy of
data sheet;
local PDF copy of instruction manual) by
Sixnet (cost is about USD$850,
purchase
order). This
device has eight (8) inputs that can be used for either voltage or 4-20
ma A/D conversion. It requires 10-30 VDC power and communicates
through an Ethernet CAT-5 connector. We use one input in 4-20 ma mode
to read the focus encoder and one input in 0-5 V mode to to read the AD592 temperature sensor.
This device operates between -30 to +70 C in 5% to 95% relative humidity, non-condensing. From the Sixnet website:
EtherTRAK Mechanical Dimensions
ET-8INS Wiring Diagram
ET-8INS
Performance Specifications
|
Number of channels
|
8
|
|
Lowest voltage range
|
+/- 0.062 Volts
|
|
Maximum voltage range
|
+/- 10 Volts
|
|
Auto-polarity current range
|
4-20 mA and 0-20 mA
|
|
Thermocouple types (see note 1)
|
J,K,E,R,T,B,C,N,S
|
|
A/D resolution
|
16 bits (0.003%)
|
|
Full scale accuracy (@20°
C)
|
+/- 0.02%
|
|
Input span & offset adjustability
|
+/- 25%
|
|
Span & offset temp. coefficient
|
+/- 30 ppm per ° C typical
|
|
Voltage range input impedance
|
200K Ohms
|
|
Current range input impedance
|
100 Ohms
|
|
CMRR (at 50/60 Hz)
|
140 dB
|
|
DMRR (at 50/60 Hz)
|
66 dB
|
|
Common mode input voltage
|
+/- 25 VDC between two input terminals
|
|
Common mode input voltage
|
1200 Volts between inputs and ground
|
|
No damage input voltage
|
+/- 50 VDC
|
|
Typical scan rate (all 8 channels)
|
800 mS - 1,000 mS, depending on
|
|
using 100 mS / channel mode
|
signal types (revised 6/30/04)
|
|
(See Notes 2 and 3 below)
|
|
|
Typical scan rate (all 8 channels)
|
300 mS - 500 mS, depending on
|
|
using 60Hz-50 mS / channel
mode
|
signal types (revised 6/30/04)
|
|
(See Note 2 below)
|
|
|
Typical scan rate (all 8 channels)
|
400 mS - 600 mS, depending on
|
|
using 50Hz-50 mS / channel
mode
|
signal types (revised 6/30/04)
|
|
(See Note 2 below)
|
|
|
Fastest scan rate (all 8 channels)
|
100 mS (revised 6/30/04)
|
|
using 16 mS / channel mode
|
|
|
(See Note 2 below)
|
|
|
|
|
|
Ethernet communications
|
See
System Specs
|
|
Isolation (from Ethernet port)
|
1200 Volts RMS 1 Minute
|
|
Required supply voltage
|
10-30 VDC (1.6 watts typical)
|
|
Operating temperature range
|
-30 to 70° C
|
|
Storage temperature range
|
-40 to 85° C
|
|
Humidity (non-condensing)
|
5 to 95%
|
|
Flammability (module plastic)
|
UL 94V-0 materials
|
|
Electrical safety
|
UL 508, CSA C22.2/14; EN61010-1 (IEC1010), CE
|
|
EMI emissions
|
FCC part 15, ICES-003, Class A; EN55022, CE
|
|
EMC immunity
|
EN50082-1 (IEC801-2, 3, 4) CE
|
|
Surge withstand
|
IEEE-472 (ANSI C37.90)
|
|
Vibration
|
IEC68-2-6
|
|
Hazardous locations
|
UL 1604, CSA C22.2/213-M1987, (Class I, Div 2, Groups A,
B, C, D), EN50021 (zone 2)
|
|
Marine/offshore locations
|
Det Norske Veritas (DNV) No. 2.4 (Class A and B)
|
Notes:
-
Thermocouple inputs are cold-junction compensated and
reported as °F
or °C.
-
These specifications apply to ET-8INS modules manufactured
afterJuly 30, 2004. Performance characteristics of earlier modules may
be different. Consult the factory for more information.
-
The default analog input integration time for this module
is 100 mS per channel. This mode is recommended for all applications
where moderate noise filtering is desirable.
Specifications are subject to change.
Consult the factory for the latest information.
Mounting brackets
LVDT bracket (click for PDF):
Positek P103 bracket (click for PDF):
Reference surface (click for PDF; this should be re-built to move the plunger down a bit):
EtherTRAK chassis
EtherTRAK mounting base (click for PDF):
EtherTRAK front panel (click for PDF):
Wiring and cables
Assembled chassis
A front view of the assembled A/D converter chassis: The
large yellow cable supplies 24 VDC power to the chassis. This connects
back to the power supply in the LDSS motion control chassis under
the platform.
There are five smaller panel connectors. The
leftmost is 24 VDC output to the LDSS shutter controller (gray cable).
This connection replaces the previous cable and connector in this area
of the instrument, and is the only 4-pin connector on the panel.
The
next connector to the right, with the black cable connected, is the
LVDT input. The LVDT is the large cylinder at the right of the photo.
The
next connector to the right, with a gray cable, is the AD592 temperature sensor,
which can be seen on top of the LVDT at the end of the gray cable.
This photo above shows the front panel without the cables connected. The two spare connectors are not wired to anything.
This is a rear quarter view of the EtherTRAK chassis in the lab.
This is a closeup of the AD592 temperature sensor cable.
The
new focus encoder is seen at the right in this internal view of LDSS.
The new items are the focus encoder chassis and the temperature sensor.
We left the old focus encoder translator in the instrument but
disconnected power and the old SLVC sensor.
View of the new LVDT focus encoder inside LDSS.
Testing
Lab testing
We
mounted a micrometer head next to the P103 LVDT and connected the
EtherTRAK ET-8INS to measure the output scale,
repeatability, and stability.
We measured the output
scale to
be 103.4 DN for 0.001 inches displacement (0.2457 microns per DN, but
we use a slightly different number in the observer software). The
data in the table below are shown to the nearest 10 ADU. The
digitization is finer than we could read on the micrometer head, but by
resetting the micrometer carefully we saw repeatability to +/-5 DN (the
LVDT is a better sensor than the micrometer). From these coarse
measurments, we find that the system is linear to at least 3.6 data
numbers (0.88 micron). A relative positioning
requirement of +/-4 microns (+/-16 DN) is
desired, so this device is adequate. A motor step is 1.25
microns (measured at LCO), so +/-4 microns is +/-3.2 motor
steps.
Jiggling
wires severely
on the LVDT did not affect the readout, nor did varying the supply voltage by 10%.
DN readout vs. P103 encoder shaft
extension
| Shaft position
(inches) |
Data number | Deviation from linear regession |
| 0.000 |
4150 | -1 |
| 0.025 | 6730 | -5 |
| 0.050 | 9320 | 1 |
| 0.075 | 11910 | 6 |
| 0.100 | 14490 | 2 |
| 0.125 | 17070 | -2 |
| 0.150 | 19660 | 4 |
| 0.175 |
22240 | 0 |
| 0.200 |
24820 | -5 |
| 0.250 |
29990 | -3 |
| 0.275 |
32580 | 3 |
Testing at LCO
After
installation in LDSS, while testing in the Aux building, we ran the
camera focus to the limits by hand and found these data numbers at
the limits:
- 25700 with the camera farthest from the CCD
- 21620 with the camera closest to the CCD
The
total range is 25700-21620=4080 units. At 0.246 microns per unit, the
total focus travel is thus 4080x0.246=1003.7 microns or about 1 mm.
The
number reported on the LDSS3 control GUI is the encoder number
multiplied by 0.2464. (This scale factor of 0.2464 is slightly
different from the actual value of 0.2457 because we set the software
value on an early two-point scale measurement in the lab rather than
the above linear fit.) So the extreme limits are 6332 (25700*0.246) and
5327 (21620*0.2464). In software, we limit the available range to be
between 5400 and 6300.
During
the day, over a period of a few hours, we noticed gradual drifts of a
few tens of data numbers (10 data numbers is 2.46 microns). We assume
this is due to temperature changes causing expansion and contraction of
the instrument.
N.B.:
These numbers may change if we replace the reference bracket to
eliminate a shim that was installed to get us within range.
We
confirmed operation of the spare temperature sensor (already cabled).
The spare reads to within 0.1 C of the installed item at room
temperature. We noticed a small self-heating effect on hookup.
A scan through focus by Jorge Bravo is presented in the
summary report.
Installation plan for LDSS focus encoder and thermometer upgrade
We will need from the site before July 12, 2008:
- An IP address for the A/D converter on-board LDSS (similar in range to the Fraba wheel encoders in LDSS) (DONE)
- A 24 VDC regulated power supply (lab supply is OK), with clip leads
- Crossover ethernet cable, any length
- Ethernet connections and cables (2 in the aux building, one new one at LDSS location)
- Metric Allen key, ball end
- Power drill
- Tap wrench
- Cutting oil
- Soldering station
- Solder
- Isopropyl alcohol
- Small cable ties
Before Pasadena staff (AU) arrives on July 13, 2008:
- Inform AU & CB of IP address to use for the A/D converter (DONE)
- Transport LDSS to the upper level of the auxilliary building (site staff; DONE)
- Collect equipment and supplies noted above (DONE)
After Pasadena staff arrival:
- We will need occasional help from an electronics person and a mechanical person
- Change the IP address of the EtherTRAK module (AU; plan to do this before shipping the equipment; DONE)
- Meet with instrument specialist, instrument scientists, electronics tech, etc., to inspect and understand the hardware (DONE)
- Confirm the IP address by email or phone with Christoph (AU; DONE in Pasadena)
- Open LDSS, remove the grism wheel (site staff, AU; DONE)
- Remove and box the existing SLVC components (site staff, AU; DONE)
- Connect
the encoder testing setup, temperature sensors, and A/D
converter to the LDSS network on the platform and verify that it
still works (AU, CB in Pasadena, Monday July 14; DONE in the aux building)
- Drill and tap mounting holes for sensor readout chassis in the LDSS body (site staff; DONE)
- Mount the sensor readout chassis (this contains the A/D converter and panel receptacles for sensors) (AU; DONE)
- Build
cable for 24 VDC supply connection (may need to trace cable to the
shutter panel to identify + and - wires) (Jones; DONE)
- Connect a 24 VDC lab supply to confirm A/D power-up (AU; DONE)
- Disconnect 24 VDC supply (AU; DONE)
- Attach the AD592 temperature sensor to the camera body with Kapton tape (AU; DONE)
- Dress AD592 wiring and plug it into the A/D chassis (AU; DONE)
- Install the new LVDT brackets (use Bellevilles; AU; DONE by Navarrette)
- Install LVDT (AU; DONE by Navarette)
- Plug in Ethernet CAT-5 cable to the A/D converter and run it to the exit panel on LDSS (AU; DONE)
- Plug in A/D Ethernet connection to the network (AU; DONE)
- Plug in a laptop to the network (AU; DONE)
- Connect the 24 VDC lab supply and power-up A/D chassis (AU; DONE)
- Verify that the temperature sensor and LVDT are active (AU uses vendor software on his laptop; DONE)
- Install LDSS on the telescope (Site staff; DONE)
- Work with Christoph on the phone to get the software calibrations, etc. (AU. CB in Pasadena; Wednesday July 16; DONE)
- On-sky testing in the early PM during the engineering run (DONE)
Shipping manifest
| Line | Qty | Description |
| 1 | 1 | P103 LVDT bracket |
| 2 | 1 | Encoder reference bracket |
| 3 | 2 | Kapton tape spools |
| 4 | 1 | Blue ethernet cable, 2 m long |
| 5 | 1 |  Spare 3-wire bulkhead power connector (Remke 303P0010N1) |
| 6 | 2 |  Yellow 3-wire cables (Remke 703A0131D1) |
| 7 | 1 | Wired AD592 temperature sensor with plug and 1 m cable (AU will hand-carry the spare) |
| 8 | 4 | 10 K ohm 1/4 watt metal film resistors |
| 9 | 1 | 4-wire cable from chassis to shutter power, 1 m (might not be long enough) |
| 10 | 12 | Belleville washers |
| 11 | 2 | Ethernet passthrough couplers |
| 12 | 1 | Spare 3-wire cable plug |
| 13 | 1 | Spare 4-wire bulkhead receptacle |
| 14 | 1 set | Assorted M4 screws (6,8,10 mm) |
| 15 | 1 | Spare 3-wire bulkhead receptacle |
| 16 | 2 | #29 drill bits |
| 17 | 2 | Taps for 8-32 |
| 18 | 1 | P103 LVDT, cabled, with micrometer head testing jig |
| 19 | 1 | Spare EtherTRAK A/D converter with software CD |
| 20 | 1 | LDSS focus encoder set (EtherTRAK in chassis with connectors, ground strap) |
| 21 | 6 | 8-32 x 3/8 SHCS |
Installation report
Summary
The
existing SLVC encoder was removed from the instrument and replaced with
the LVDT encoder. The old transducer electronics remain in the
instrument and new communications electronics were installed. A
summary report (PDF) was submitted to the LCO techncial group.
Sunday, July 13, 2008
Uomoto
arrived in the afternoon. LDSS was already in the aux building. Navarrette, Merino, and Uomoto
opened the instrument and
removed the grism wheel and motor mechanisms. We removed the old SLVC
encoder and its mounting hardware and Navarrette installed the mounting
hardware for the new LVDT system. Quiroz, Alfaro, and Cortes
drilled and tapped the mounting holes for the chassis in the side of
the instrument.
Monday, July 14, 2008
We mounted
the new electronics in LDSS and installed the sensor cables. We used an ethernet
switch to connect a laptop and the EtherTRAK to the network. We used a lab supply to put 24 VDC on the EtherTRAK chassis. After
power-up, we used the SIXNet IO Tool Kit to verify that the
EtherTRAK and sensors were working.
Birk in Pasadena then confirmed that he could read the EtherTRAK device with his software.
The
LVDT reading was near the end of travel, such that we went to the 15
bit limit before the end of travel. Uomoto will make a new
reference plate that's 1 mm lower. In the meantime, some aluminum tape was stacked to make a shim.
Jones removed three LED
status lights from the EtherTRAK board to make it dark. I had
previously confirmed with SIXNet (talked to "Andrew") that this would
not affect the operation. It voids the warranty, however. The LED lights in the spare EtherTRAK were not removed.
Jones made new cables. These provide the 24 VDC from the motor controller
chassis to the focus encoder and 24 VDC from the focus encoder chassis
to the shutter controller. Previously, the 24 VDC from the motor
controller chassis was used only to power the shutter controller. The
24 VDC to the shutter controller simply passes through the focus
encoder chassis.
We confirmed operation of the spare temperature sensor (this was not available before shipping).
Tuesday July 15, 2008
Merino,
Quiroz, and Uomoto reassembled LDSS in the aux building and Quiroz
drilled two holes for a temporary mounting location for an Ethernet
switch.
LDSS was rolled out to the Clay dome under the
aluminizing tank (Quiroz, Alfaro, Merino, Navarrette) and re-installed
on the telescope.
Bravo & Cerda installed the cables and
Cortes installed a power cable for the Ethernet switch. In the end,
however, there were enough Ethernet cables in the cable wrap to avoid
using the Ethernet switch.
Birk communicated with the focus encoder from Pasadena.
Wednesday July 16, 2008
Birk
(Pasadena) & Uomoto (Las Campanas) confirmed that the focus encoder
could be commanded from the modified LDSS gui and scaling factors and
signs were confirmed. The range of focus motion was set to 5400 to 6300
units (microns) on the LDSS screen. This range is off the camera travel
limits by about 1/6 turn of the motor. Birk downloaded the new software to Guanaco and Zorro.
Bravo
& Uomoto operated the software but Cryotiger problems prevented
gettting data tonight. Covarrubias arrived in the early evening.
Thursday July 17, 2008
Bravo
measured focus values for many filters and found that the recorded
offsets (wrt SDSS r) were far from the previous "correct" values.
IP addresses in LDSS:
Parts list
| Line | Qty | Spares | Catalog picture | Description | Manufacturer/Part no. | Vendor/Vendor no. | Cost | Notes |
| | | | | | | | |
| 1.00 | 2 | 1 |  | 3-conductor male plug for sensor cables | Hirose / MXR-8PA-3PB(71) (local copy) | Digikey / HR1821-ND | 16.03 | Cable ends from AD592 temperature sensor and Positek P103 LVDT |
| 2.00 | 1 | 0 | | 4-conductor male plug for shutter cable | Hirose / MXR-8PA-5PB(71) (local copy) | Digikey / HR1822-ND | 16.29 | Cable end from shutter panel to chassis |
| 3.00 | 2 | 1 |  | 3-conductor female receptacle for sensor cables | Hirose / MXR-8RA-3S(71) (local copy) | Digikey / HR1826-ND | 8.83 | Front panel connectors for AD592 temperature sensor and Positek P103 LVDT |
| 4.00 | 1 | 1 | | 4-conductor femail receptacle for shutter cable | Hirose / MXR-8RA-4S(71) (local copy) | Digikey / HR1827-ND | 9.64 | Front panel receptacle for shutter cable |
| 5.00 | 1 | 1 | | 3-conductor female plug, single keyway, external thread, for 24 VDC input power | Remke 703A0131D1 | McMaster / 3214K42 | 37.72 | Front panel connector for incoming 24 VDC from power supply in the motion control chassis. |
| 6.00 | 1 | 1 | | 3-conductor male receptacle, single keyway, external thread, for 24VDC input power | Remke 303P0010N1 | McMaster / 3214K44 | 23.27 | Cable end for incoming 24 VDC from the SOLA supply in the motion control chassis to the front panel power input. |
| 7.00 | 1 | 1 |  | Temperature transducer in TO-92 package, 1 micro-amp/K | Analog Devices / AD592BNZ (local copy) | Digikey / AD592BNZ-ND | 10.82 | One of these temperature sensors is taped to the camera barrel and the other [?] |
| 8.00 | 1 | 1 |  | LVDT with 4-20 ma output, 10 mm stroke | Positek / P103.10EL100NRT | Everight Precision / P103.10EL100NRT | 620.00 | LVDT to measure position of the LDSS camera relative to the LDSS body |
| 9.00 | 1 | 1 | | 8-port 16-bit A/D with Ethernet communications | Sixnet / ET-8INS-U | Sixnet / ET-8INS-U | 850.00 | Instrumentation module to read 4-20 ma current loops and voltages with Ethernet |
| 12.0 | 1 | 0 |  | Ethernet patch cable, 2 m, blue | Assmann / A-MCUP-80020/B-R (local copy) | Digikey / AE9947-ND | 5.18 | Ethernet cable from the A/D chassis to the outside wall of LDSS (not long enough; used one from LCO stock) |
| 13.0 | 1 | 1 |  | Ethernet CAT5E inline coupler | Assmann / A-TA3534-R (local copy) | Digikey / AE10093-ND | 8.02 | Interface to the external Ethernet cable |
| 14.0 | 1 | 1 |  | 8-32 steel hand tap | Greenfield 15284 | McMaster / 2522A718 | 3.61 | Tap for cutting holes in LDSS to mount A/D chassis |
| 15.0 | 1 | 1 |  | Drill bit, size 29 | N/A | McMaster / 30585A42 | 1.12 | Drill bit for tapping holes in LDSS to mount A/D chassis |
| 16.0 | 1 | 1 |  | Kapton tape | N/A | McMaster / 7639A62 | 6.72 for a 5-yard roll | Low-static tape for AD592 sensor placement |
| 17.0 | 6 | 6 |  | Belleville disk springs | Gardner Spring MB0281-010 | McMaster / 9712K11 | 5.07 for 12 | Help prevent the LVDT and reference bracket from coming loose |
| 18.0 | 4 | some |  | M4 x 8 mm shcs | Brikksen
| McMaster / 91292A108 | 6.01 for 100 | Attach LVDT brackets to LDSS |
| 19.0 | 2 | some |  | M4 x 10 mm shcs | Brikksen | McMaster / 91292A116 | 6.35 for 100 | Attach LVDT bracket to LDSS |
| 20.0 | 1 | 8 |  | 10 K ohm metal film resistor, 1/4W, 1% | ? | Digikey / P10.0KCACT-ND | 0.171 ea | Drops voltage from AD592 for EtherTRAK signal |
August 14, 2008
Alan Uomoto, Jennifer Marshall, Christoph Birk, Jorge Estrada
