Centroid Products is in the process of changing from its original analog electronic senders to programmable digital senders.  Though the senders' appearance and outputs are the same (ohms, volts, or milliamps), the programmable style senders have the following advantages:



Because the output range of the sender can be programmed after the sender is completed, it allows us to stock generic unprogrammed senders and program them as needed to fill an order.



Centroid senders work by measuring capacitance.  The dielectric constant of gasoline with ethanol is higher than for standard gasoline, leading to a higher reading.  The programmable senders have a Full Detection feature to detect a full tank and scale the readings accordingly.  This corrects for the ethanol factor.  For the analog senders, the Full adjustment had to be corrected in the field manually.



Centroid's analog senders could be designed to correct for non-rectangular tank shape.  But they did so by approximating the tank curve with two straight lines.  The programmable senders allow for approximating by 9 straight lines for a closer fit.  Also, because the correction is done by software in the sender rather than extra hardware as the analog senders required, there is no $15 additional charge per sender.



The programmable senders can be provided with averaged readings ("damping") like the analog senders, but there is no extra $7 charge because no extra hardware is required.



The alarm output of the programmable sender can be provided in the following modes:  none, low, high, low and high, high-on/low-off, low-on/high-off.  Also, momentarily touching the alarm terminal to ground while the alarm is on will shut off the alarm until the next alarm condition.  This is convenient for audible alarms.  Alarms are set at the factory for the requested percentage rather than adjusted in the field as with the analog senders.



Our preference is to provide the senders at the correct length to match your tank.  However, the senders have always been shortenable in the field.  There was a limit to the amount they could be shortened, however.  For example, a 24" sender could only be shortened to as little as 12".  The 2-to-1 limit in shortening was due to a tradeoff in calibration-adjustment "touchiness" versus range of shortening.


The programmable senders are calibrated by a scheme of shorting the Send terminal to Negative during powerup rather than a mechanical potentiometer adjustment.  Doing away with mechanical adjustment removes the touchiness factor, so there isn't a limit to shortenability. 

Click here for the calibration instruction sheet.


\\joel\c\joel\word\prog-senders.htm    12/5/08