Frequently Asked Questions

How can I control what is displayed by the IOTA-VTI?

What does the TV Safe/Full Screen switch do?

Why is field count included in the Time display?

Why does it sometimes take longer to get a fix than at other times?

Why does the 'Internal' item on the Position screen flicker between Internal and External when no camera is connected?

How do I monitor the NMEA sentences used by my IOTA-VTI?

Why was non-volatile memory added to the IOTA-VTI v3?

Why, after hooking up my complete video system, is there no time display?

Why is the GPS Latitude and Longitude wrong?

Why do I get an error message when my nearby beer fridge starts up?

Why does the vSync time not always display 16840 us?

What is HDOP?

What does the Almanac 11h 2011-03-17 line mean?

What models are available?

What accessories are available for the IOTA-VTA v3?

How much does IOTA-VTI cost?


Frequently Asked Questions - Earlier Models

Why is the GPS inside the enclosure for the IOTA-VTI Basic model?

Can I convert my Basic IOTA-VTI to an EX or Dual?

Can I convert my EX model IOTA-VTI to a Dual?

 

Q. How can I control what is displayed by the IOTA-VTI v3?

A. Most often the user will want to display and record in the Time mode, which stamps UTC hours, minutes, seconds, deci-milliseconds and field count on each video field. Using a front-panel switch, the user can select the Position mode to display and record: GPS status; UTC hours, minutes and seconds; latitude, longitude and elevation; and other system parameters. The transition from Time to Position and back to Time can be completed within 10 seconds if desired. Some users will prefer to make longer records of the information provided in the Position mode. It is good practice to record the Position screen before and after timing an occultation or other event.

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Q. What does the TV Safe/Full Screen switch do?

A. The TV Safe/Full Screen switch controls the vertical positioning of the information on the screen. In Full Screen mode, time is written very near the bottom of the screen, and an overscan feature in many recorders and monitors may cause the time line to be only partially visible. If your system displays time suitably in Full Screen mode, it is recommended that you use the system that way, because it leaves more of the screen available to display your image. If Time is not readily visible in Full Screen mode, use the TV Safe mode. It is necessary to press the Reset switch (or cycle power off and on) for a change in the position of this switch to take effect.

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Q. Why is field count included in the Time display?

A. Field count is a means of verifying the integrity of a record. Data analysis software can read time and field count for each frame and field in a video record, and write that information to a spreadsheet. A plot of field count versus time will then reveal any dropped frames.

Field count can also be used to accurately establish time for an event that is recorded before a fix has been obtained. If there is no fix, the field count will be accompanied by a series of xxxx in the time display. When a fix is obtained, the xxxx will be replaced with valid time, and the field count can be used to extrapolate backward to determine a valid time for any field count. Field count starts at zero when power is first applied, and it is reset to zero when the Reset button is used. The process of changing from Time to Position and back to Time does not reset the field count, but it does interrupt it, for about three seconds. Backward extrapolation through a Time-Position-Time cycle will therefore be only approximate.

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Q. Why does it sometimes take longer to get a fix than at other times?

A. It may take a few minutes for the GPS to get its first fix, depending on how much of the sky is visible to the GPS and how far the unit has been transported from its previous fix, but subsequent fixes will usually require a minute or less.

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Q. Why does the 'Internal' item on the Position screen flicker between Internal and External when no camera is connected?

A.  Because no camera is connected.  The input line then picks up stray noise, some of which may look briefly like a video signal.  Hence the flicker.

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Q. How do I monitor the NMEA sentences used by my IOTA-VTI v3?

A. The serial dongle accessory will allow recording of the NMEA sentences coming from the GPS, creating a text file. The dongle will have a standard USB plug for connecting to a computer and a 3.5-mm plug to connect to the IOTA-VTI v3. To use the dongle, you will need to have a computer equipped with a USB A port, and with a terminal emulator program installed. (Suitable terminal emulator software is available from various sources, some of them allowing free downloads.) The GGA sentence will be recorded each second when the IOTA-VTI v3 is in Time mode, and the GGA and ZDA sentences will be recorded at three-second intervals when the IOTA-VTI v3 is in Position mode.

When using the terminal emulator program, the correct settings are: 57,600 8 N 1 (Baud rate: 57,600 HZ; Data bits: 8; Parity: None; Stop bits: 1).

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Q. Why was non-volatile memory added to the IOTA-VTI v3?

A. The non-volatile memory feature means that when leap seconds are added (the most recent one was June 30, 2015 ), knowledge of each leap second will automatically be retained beginning with next use of the IOTA-VTI v3. There is a small nuisance associated with this: a Li-ion coin cell will eventually need to be replaced. The cell used is the CR2032, which is readily available and has a long operational life. There has not yet been time to experimentally confirm, but the calculated life is over two years. Replacement will require removing the enclosure cover (4 screws). Status of the battery is announced at the bottom of the Splash Screen each time the IOTA-VTI v3 is powered on or reset.

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Q. Why, after hooking up my complete video system, is there no time display?

A. First, check the red Power light on the IOTA-VTI v3 front panel. If the LED is not on, the IOTA-VTI v3 is not receiving power. Check to see that your power plug is fully inserted at the coaxial power jack. The power plug must be center pin positive. It won't work if the polarity is reversed. If the Power LED is not lit, then you can't go further.

IOTA-VTI v3 has a fast-blow fuse (5 mm by 20 mm, 250 mA). If power is supplied outside the range of 8 to 28 volts, expect the fuse to blow. If that happens, verify that the power source is in the acceptable range before replacing the fuse.

If you have power, then switch to the Position screen, and press the Reset button. You should see the video display flicker then light up with the splash screen.

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Q. Why is the GPS Latitude and Longitude wrong?

A. Take careful note of the Operations Manual, Page 2 (Overview/Position Screen). Latitude and longitude are given in degrees, minutes, and decimal minutes. Thus 3345.1234 S as a Latitude means 33 degrees, 45.1234 minutes South. Do not be like the designer of the unit, who forgot this and tried to work out why Google Earth refused to display his home location correctly!

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Q. Why do I get an error message when my nearby beer fridge starts up?

A. Because the fridge is putting out electrical interference and the IOTA-VTI v3 lets you know that its operation was interfered with.

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Q. Why does the vSync time not always display 16840 us?

A. If there is no camera connected, the IOTA-VTI v3 uses a simulated camera timebase so you can see some kind of a screen. But the simulation is not a camera, and its timebase is not as precise. When a camera is plugged in, the camera timebase provides the rigor for the frame counter. The GPS provides the rigor for the UTC display. Note: The green LED on the front panel is illuminated when an external video signal is supplied.

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Q. What is HDOP?

A. Horizontal Dilution of Precision. This is an estimate of the accuracy that is associated with the positional information. As more satellites are acquired, HDOP will usually become smaller, indicating better accuracy. In general, if HDOP is less than about 2, the indicated latitude, longitude and elevation are accurate enough to meet IOTA reporting requirements. A fix involving 7 satellites or more, with an HDOP of 2 or less, should be routine, unless the unit is inside a building or other unfavorable location.

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Q. What does the Almanac 11h 2011-03-17 line mean?

A. This means that the almanac was last updated by the GPS constellation at 11 hours on March 17, 2011 (UTC). The GPS unit can forget its almanac if the power goes off for long enough. When the almanac is forgotten, the time displayed is GPS time and not UTC, as it has not accounted for all the leap seconds since the GPS was made. A recent almanac is a way for you to have confidence that the time shown is UTC.

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Q. What models are available?

A. IOTA-VTI v3 is the only current model. In use the IOTA-VTI v3 will be unchanged from the former IOTA-VTI models: the enclosure and basic switches and connectors are all the same. The most important improvements: the new GPS is more sensitive, and will have a non-volatile memory.

There are three earlier models which are no longer available for purchase: The Basic model with an internal GPS, the EX model with an external GPS and the Dual model with both an internal and an external GPS.

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Q. What accessories are available for the IOTA-VTA v3?

A. Two accessories will be available as options: an external antenna ($14) and a serial dongle ($29). Every IOTA-VTI v3 will have connectors to accept both of the accessories, so either accessory can be purchased later with no compatibility complications.

Q. How much does IOTA-VTI v3 cost?

A. IOTA-VTI v3 is priced at $249. Only US dollars are accepted. Shipping and handling charges will be added. Sales tax of 9.25% will be added for shipments to California addresses. Payment will be accepted via PayPal (credit cards or use your PayPal account).   Order Now!

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The following questions apply to earlier models, which are no longer being sold:

Q. Why is the GPS inside the enclosure for the IOTA-VTI Basic model?

A. Because the GPS is sensitive enough to work even though it is inside the enclosure, and small enough so that it does not compromise the other elements in the design. Common practice has been for video timing devices to use a GPS that has an attached cable some meters in length, so that the GPS can be positioned for a minimally-obstructed view of the sky with little consideration for where the remaining system components are located. The high-sensitivity USGlobalSat EM-406A GPS used in the IOTA-VTI Basic readily acquires satellites even when positioned with less-than optimal sky visibility. With the GPS inside the enclosure, IOTA-VTI Basic becomes a very compact system, with external cables required only for power and the video input and output.

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Q. Can I convert my Basic IOTA-VTI to an EX or Dual?

A. No. Circuitry required to access the external GPS is not present in the Basic version.

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Q. Can I convert my EX model IOTA-VTI to a Dual?

A. Yes. The only difference between the EX and Dual is whether the internal GPS (a USGlobalSat EM-406A) is present. The EX has the socket necessary to plug in that GPS, and a unit need not be returned to Video Timers to make that addition.

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