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CiES Fuel Level Sending Units - Installation and Configuration for SkyView

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cies-fuel-tank-senders.jpg
ℹ️ OVERVIEW: CiES magnetoresistive fuel senders provide high-accuracy fuel level measurement for SkyView systems. This guide covers proper wiring, configuration, and calibration procedures specific to Dynon SkyView integration.

Understanding CiES Fuel Sender Technology

CiES fuel senders use patented magnetoresistive technology that measures the magnetic field direction at the pivot point of the float arm, rather than using traditional resistive wiper contacts. This design offers several advantages:

  • No mechanical contact between the float mechanism and electronics
  • Electronics remain outside the fuel volume for improved safety
  • Greater angular travel range (up to 175°) compared to traditional senders
  • No degradation from mechanical wear or vibration
  • Higher precision throughout the sender's operational life

The magnetic field is generated at the float arm pivot point, and an electronic compass inside the sender body (outside the fuel) measures the field direction. This contactless design eliminates friction and maintains precision regardless of mechanical movement or vibration.

CiES Sender Versions

CiES currently offers two versions of their fuel senders:

  • Frequency output (base model): Uses blue wire for digital frequency signal output
  • Frequency + Voltage output: Adds green wire with 0-5V analog voltage output plus frequency on blue wire
🚫 CRITICAL: SkyView and SkyView HDX systems require CiES senders with voltage output capability (green wire). The frequency-only models are not compatible with SkyView EMS modules. Verify your CiES sender part number includes voltage output at purchase or before installation.

Prerequisites

  • SkyView system with SV-EMS-220 or SV-EMS-221 module
  • CiES fuel senders with voltage output (green wire) - part numbers ending in -**5 or -5**
  • Access to fuel tanks for sender installation and calibration
  • Fuel measurement containers accurate to within 3% for calibration
  • SkyView System Installation Guide (for reference)
  • CiES Installation Manual specific to your aircraft model
  • Basic electrical testing equipment (multimeter with voltage measurement)

Step 1: Select Appropriate EMS Input Pins

CiES voltage output senders should be connected to specific EMS module pins that support disabling internal pull-up resistors.

1A. Enhanced General Purpose Inputs (Recommended)

Use these pins on the SV-EMS-220/221 for CiES sender installation:

  • Pin 22 - Enhanced General Purpose Input
  • Pin 23 - Enhanced General Purpose Input
  • Pin 31 - Enhanced General Purpose Input
  • Pin 8 - Enhanced General Purpose Input (if available; typically used for fuel pressure)
ℹ️ FIRMWARE-SPECIFIC CONFIGURATION:
  • SkyView HDX (Firmware 17.5 or later): Select FUEL LEVEL (CIES) as the sensor type
  • SkyView Classic (Firmware 16.7.8 or later): Select FUEL LEVEL (CIES) as the sensor type
  • Earlier firmware versions: Select FUEL LEVEL (CAPACITIVE) as the sensor type
The FUEL LEVEL (CIES) option is only available on Enhanced General Purpose inputs and provides the same functionality as FUEL LEVEL (CAPACITIVE) with more descriptive naming.

1B. Standard General Purpose Inputs (Use With Caution)

If Enhanced GP inputs are unavailable, standard GP inputs (pins 4, 7, 9, 10, 11, 20, 21) may be used with the following limitation:

🚫 CRITICAL: Standard GP inputs cannot disable their internal pull-up resistors. If a CiES sender loses power when connected to a standard GP input and configured for FUEL LEVEL (RESISTIVE), the system will fail to a FULL indication (5V) rather than EMPTY (0V). This is an undesirable failure mode that can mask fuel system problems. Use standard GP inputs only if Enhanced GP inputs are completely unavailable.

Step 2: Physical Installation Notes

Bonding Requirements (Metal Aircraft and Metal Tanks Only)

🚫 CRITICAL: This guide highlights SkyView-specific configuration requirements and common installation challenges only. For complete installation procedures, safety requirements, and aircraft-specific details, installers must reference the applicable CiES installation manual for their aircraft model.

For aircraft with metal structure or metal fuel tanks, proper bonding is critical for lightning protection:

Method 1: Direct Bonding Through Mounting Hardware

  1. Select one mounting screw location
  2. Burnish (remove) the anodize coating at that location using light abrasion
  3. Install the mounting screw at that location
  4. Measure resistance from the screw head to a known aircraft ground
  5. Verify resistance is less than 0.03 Ω (thirty thousandths of an ohm)

Method 2: Separate Bonding Strap

  1. Select one mounting screw location
  2. Burnish the anodize coating at that location
  3. Install a bonding strap with ring terminal under the screw
  4. Connect the other end of the bonding strap to nearby grounded aircraft structure
  5. Measure resistance from the screw head to aircraft ground
  6. Verify resistance is less than 0.03 Ω
🚫 CRITICAL: Proper bonding prevents ignition sources in the event of a lightning strike. This is a mandatory safety requirement for metal aircraft and metal fuel tanks. Do not skip this step.
CiES fuel sender bonding diagram showing ground strap installation

Step 3: Wiring Installation

3A. Power and Ground Wiring

CiES senders require aircraft DC power to operate:

  1. Route the Red wire (power) to aircraft bus through appropriate circuit protection
  2. Use 1-2 amp circuit breaker or fuse per AC 43.13-1B Section 4 Table 11.3
  3. Route the Black wire (ground) to a verified aircraft ground point or an available EMS ground wire (pins 5, 13, 16, 17, or 30)
  4. Verify ground resistance is less than 0.3 Ω to aircraft battery negative terminal
  5. Follow existing fuel sender wire routing paths when possible
  6. Use M22759/11-20-X wire or aircraft-approved equivalent for new wire runs
⚠️ IMPORTANT: The sender body is NOT a ground. The Black ground wire must be connected to a dedicated aircraft ground point or EMS module ground wire. Poor grounding will cause erratic or floating voltage readings, especially on analog voltage senders.

3B. Signal Wire Connections

Connect the appropriate CiES output wires to the EMS module:

  • Green wire - 0-5V analog voltage output → Connect to EMS Enhanced GP input (pins 22, 23, 31, or 8)
  • Blue wire - Digital frequency output → Can be used for diagnostics or future compatibility (cap and stow if not used)
  • Gray wire - Used with multi-sensor installations in a single tank.
cies-ems-hookup.jpg
⚠️ IMPORTANT: When capping and stowing blue and gray wires, be sure to stow them separately and not bundled together. If the two wires are able to make contact with each other it can cause incorrect readings and unstable fuel level indication behavior. 

3C. Multi-Sender Tank Configurations

For tanks requiring multiple senders, wire them in master/slave configuration:

  • The most inboard sender is the master
  • Outboard senders are slaves
  • Connect slave sender Orange/Red wire to master sender Orange/Red wire
  • Connect slave sender Gray wire to master sender Gray wire
  • All senders share common Red (power) and Black (ground)
  • Only the master sender Green wire connects to the EMS module
CiES Triple Sensor Example

3D. Ground Verification Procedure

If the sender produces erratic or changing voltage output:

  1. Locate the aircraft battery negative terminal
  2. Run a temporary jumper wire from the sender Black ground wire directly to battery negative
  3. Power up the system and check sender operation
  4. If operation is now stable, the original ground connection is inadequate
  5. Relocate the ground connection to a better ground point with lower resistance

Step 4: SkyView EMS Configuration

4A. Configure Sensor Input Mapping

For each CiES sender connected to the EMS module:

SETUP MENU > EMS SETUP > SENSOR INPUT MAPPING
Select the PIN # where the Green wire is connected
Press EDIT

Set the following parameters:

  • FUNCTION: LEVEL
  • SENSOR: FUEL LEVEL (CIES) [Or "other" - see Step 1.]
  • NAME: LEFT FUEL or RIGHT FUEL (or AUX FUEL for auxiliary tanks)
🚫 CRITICAL: You must select FUEL LEVEL (CAPACITIVE) as the sensor type, NOT FUEL LEVEL (RESISTIVE). The CAPACITIVE setting disables the internal pull-up resistor on Enhanced GP inputs. Using RESISTIVE will cause false full readings when the sender loses power. See Section 1B for more information.

Step 5: Pre-Installation Verification Testing

⚠️ IMPORTANT: With the sender now configured in the EMS, verify proper operation before installation. Hold the sender in your hand in the correct orientation relative to the tank installation. Power up the system and manually move the float arm through its full range of motion while monitoring SENSOR DEBUG DATA. Verify voltage changes smoothly from approximately ~0.1V (empty position) to ~4.7V (full position). This bench test prevents time-intensive troubleshooting after installation. More information below.

5A. Verify Sender Output

With the sender wired and configured but not yet permanently installed:

  1. Ensure the sender is connected to the configured EMS pin
  2. Ensure aircraft power (Red wire) and ground (Black wire) are connected
  3. Position the sender in the correct clock orientation for your tank (12, 3, 6, or 9 o'clock)
  4. Navigate to: SETUP MENU > EMS SETUP > SENSOR DEBUG DATA
  5. Monitor the CAL (V) and VALUE columns for the configured pin
  6. Move the float arm through its full range of motion
  7. Verify voltage changes from near ~0.1V (empty position) to near ~4.7V (full position)
⚠️ CRITICAL PRE-INSTALLATION CHECK: Before final installation, verify the float arm has full clearance to move through its entire range without contacting internal tank structure, bladder folds, or other obstacles. The float arm may be gently bent to clear obstructions per the CiES installation manual. Failing to verify clearance before installation can result in: draining the tanks, removing the sender, bending the float arm, reinstalling, re-sealing, and re-calibrating the entire fuel system. Check clearance now to avoid significant time and expense later.

5B. Test Failure Modes (Pre or Post-Calibration)

Verify proper failure behavior by testing both powered and unpowered states:

  1. With sender powered and connected, note the voltage reading
  2. Disconnect power (Red wire) from the sender by pulling the circuit breaker.
  3. Verify the system shows 0V or near 0V (empty indication) rather than 5V (full indication)
  4. Reconnect power and verify normal operation resumes

This test confirms that a power failure will result in an empty indication rather than falsely showing full tanks.

5C. Final Permanent Installation

Once testing confirms proper operation:

  1. Ensure the sender sits flush against the tank mounting surface
  2. Verify the float arm has clearance and moves freely through full range
  3. Torque all mounting fasteners to 18-22 in-lbs using a crossing pattern
  4. Verify bonding resistance is less than 0.03 Ω (metal aircraft only)
  5. Re-check that the float arm still moves freely after final torquing if you have access through the tank filler.

Step 6: Fuel Calibration

ℹ️ NOTE: This section provides limited calibration guidance. For complete fuel system calibration procedures, see the separate guide: Configuring and Calibrating Fuel Tanks in SkyView

6A. Pre-Calibration Setup

  1. Jack and level the aircraft in a normal flight attitude
  2. Drain all fuel from the tank to be calibrated
  3. Add the unusable fuel quantity listed in the aircraft Type Certificate Data Sheet (TCDS)
✓ TIP: Use graduated fluid measurement containers accurate to within 3% for all fuel measurements. Do not rely on fuel pump dispenser readings. If measuring by weight, accurately determine fuel density and convert to volume.

6B. Calibration Process

  1. Navigate to: SETUP MENU > HARDWARE CALIBRATION > EMS CALIBRATION > FUEL TANK 1 (LEFT) (or RIGHT, AUX, Etc)
  2. Select CALIBRATE
  3. The system will prompt to fill the tank to specific fuel quantity increments
  4. Add the requested amount of fuel accurately using measured containers
  5. Allow voltage readings to stabilize before pressing ADD (may take 30-60 seconds)
  6. Continue through all calibration points hitting ADD after each pour until the tank is full
  7. After the last pour, press ADD one more time before hitting FULL to complete the process
  8. Save the calibration when complete
Sensor voltage indication to monitor while calibrating.
⚠️ NOTE: You may reach a point during calibration where adding more fuel does not change the voltage reading. This occurs when the float arm has reached its maximum physical travel due to tank structure limitations. This is normal - complete the calibration with the maximum values achieved.

6C. Post-Calibration Verification

After calibration is complete:

Last calibration point reference for rounding down
  1. Return to: SETUP MENU > HARDWARE CALIBRATION > EMS SETUP > FUEL TANK 1 (LEFT) (or RIGHT, AUX, Etc)
  2. Select EDIT
  3. Scroll to the bottom of the calibration table
  4. Note the fullest quantity listed for the tank
  5. If you have multiple tanks, verify both tanks calibrated to similar maximum values
  6. Round down to the nearest whole number where both tanks match
  7. Next navigate to: SETUP MENU > EMS SETUP > SENSOR SETUP > LEFT LEVEL (or RIGHT LEVEL, AUX, Etc)
  8. Set the Max Graphical Display value to this rounded number
  9. Save the settings
Editing Maximum Graphical Display under SENSOR SETUP

6D. Tank Capacity Matching

For aircraft with symmetrical fuel tanks (left and right):

  1. Compare the maximum calibrated values for both tanks
  2. If one tank calibrated to 49.2 gallons and the other to 50.1 gallons:
  3. Set both Max Graphical Display values to 49 gallons (the lower value rounded down)
  4. This ensures both fuel quantity displays reach "Full" simultaneously

Step 7: System Verification

7A. Functional Testing

Verify proper system operation:

  1. With tanks at known fuel levels, verify display accuracy
  2. Check that fuel quantity decreases smoothly during fuel consumption
  3. Verify both tanks indicate similarly when filled equally
  4. Test low fuel annunciations trigger at proper fuel levels (as set under SENSOR SETUP)
  5. Verify fuel quantity indication updates during aircraft attitude changes

7B. Failure Mode Testing

Test the system response to sender power loss:

  1. With the aircraft powered and fuel displays showing normal indications
  2. Pull the circuit breaker providing power to the CiES senders
  3. Verify the fuel displays show Empty or 0 gallons (not Full)
  4. Reset the circuit breaker
  5. Verify normal fuel indications return
✓ EXPECTED RESULT: Loss of sender power should result in Empty indication. If the system shows Full when power is lost, verify you are using Enhanced GP inputs with FUEL LEVEL (CIES or CAPACITIVE) sensor configuration.

Troubleshooting

Issue Possible Cause Solution
No fuel indication or stuck at 0% (or full) No power to sender or poor ground connection Verify 9-28VDC at sender Red wire. Check ground resistance <0.3Ω to battery negative. Test with temporary jumper to battery ground.
Fuel indication stuck at 100% full Sender losing power on standard GP input with RESISTIVE sensor config Rewire to Enhanced GP input (pins 22, 23, 31, or 8) and configure as FUEL LEVEL (CIES or CAPACITIVE). Verify circuit breaker is not tripping.
Erratic or rapidly changing fuel readings Poor ground connection causing voltage float Measure ground resistance. Run temporary jumper to battery negative to verify. Relocate ground to better aircraft ground point.
Fuel quantity does not change when adding fuel Float arm physically bound or obstructed in tank Remove sender and inspect. Check for tank structure, sealant, or debris blocking float movement. Verify sender mounted flush to tank surface. Minor float arm bending may be required.
Voltage inverted (5V empty, 0V full) Sender mounted in incorrect clock orientation Verify sender index hole alignment matches required orientation for tank. Remove and reinstall sender in correct position. In rare cases this could be the result of manufacturer calibration error.
Calibration cannot reach full tank capacity Float arm hitting maximum travel limit from tank structure This is normal. Complete calibration with maximum achieved values. Adjust Max Graphical Display to match actual calibrated maximum.
Left and right tanks show different values when filled equally Tanks not calibrated to same maximum or aircraft not level during calibration Verify aircraft was level during calibration. Set Max Graphical Display to same value for both tanks (use lower calibrated value). Re-calibrate if necessary.
Sender worked during testing but not after final installation Float obstruction after torquing, wiring pinched, or poor connections Check SENSOR DEBUG DATA for voltage output. Verify power and ground at sender. Check for pinched wires. Loosen fasteners and verify float has clearance through full range, then re-torque carefully.

Important Safety Notes

🚫 SAFETY: CiES senders keep all electronics outside the fuel volume for improved safety. However, proper installation practices must still be followed:
  • Use appropriate circuit protection (1-2A breaker or fuse) for sender power
  • Verify bonding requirements are met on metal aircraft and metal tanks
  • Follow all fuel handling safety procedures during installation and calibration

Reference Documents

  • CiES Installation Manual (CC-TR-2840-031) specific to your aircraft model and sender part numbers
  • SkyView System Installation Guide - EMS Configuration sections
  • Aircraft Type Certificate Data Sheet (TCDS) - for unusable fuel quantities
  • Aircraft Maintenance Manual - for specific fuel system requirements

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