device which converts the electric impulses from the load cells to mechanical motion. For electronic printers, adaptation would most likely be accomplished by replacing electronic components, such as resistors; however, if these are used with the lever-fulcrum devices, a transition device to convert mechanical motion to electrical impulses would be required, and it is possible that mechanical changes to this device could bring about the desired units change.

For electronic dials (used primarily on load cell type scales), adaptation. will require that the electronic components (particularly resistors) be replaced. Such components control the indicated capacity of the dial. Of course, present face plates with customary units would have to be replaced and the scale recalibrated. For mechanical dials, adaptation requires recalibration and, of course, new dial face plates.

For digital indicators, adaptation will require either mechanical or electronic component changes. There is a similarity in the adaptation concepts for digital indicators and printers, even though the specifics of the changes are different. (1) Digital indicators which contain a mechanical to electrical transition device can be adapted by modifying the mechanical elements (e.g., gear changes) therein. In the alternative, adaptation may be accomplished by replacing electronic components. This type of indicating system may be used with either lever-fulcrum or load cell scales. The latter types of scales require a transitional device, opposite in purpose to the one in the indicator, before this type of digital system can be used. This procedure allows load cell scales to use existing mechanical-electrical indicating devices. (2) For completely electrical indicating systems, adaptation would require only electronic component changes. These systems may also be used with leverfulcrum scales provided a load cell or similar device is attached to the appropriate part (e.g., steelyard rod, or transverse extension lever) of the lever system.

Manufacturers feel that adapting digital indicators or printers to indicate or record respectively to the nearest kilogram will be less troublesome and costly than to the nearest 0.5 kilogram, although the 0.5 kg would be closer to the 1 lb minimum graduation most often used. It should also be noted that adaptation to the smaller indication (0.5 kg) would result in a loss of one significant figure. Thus, the capacity of the indicator or printer would be reduced. For example, a four digit indicator or printer has a capacity of 9,999 lbs, whereas its adapted capacity to the nearest 0.5 kg would be 999.5 kg or 2,203.52 lbs. Such a reduction in capacity would affect the usefulness of the scale.

Finally, manufacturers feel that production and/or assembly of adapted devices will not be difficult, but that adaptation of scales now using customary units would be expensive (sec. I-7). It seems that a majority of the latter costs stem from: (1) manhours spent installing needed parts and recalibrating

9 One method which may be used to translate mechanical action into electronic impulses is to use a rotating disk which contains indications in coded form and a group of photoelectric cells. An optical system projects the disk's indications onto the photoelectric cells which in turn provide the necessary electric signals for the digital readout device. Note: A similar concept is used on prepackaging electronic computing scales.

any device; (2) the purchase of new dials, unit weights and beams for lever scales; and (3) the replacement of some printers and indicators where it is more economical to replace than to adapt.

OVER AND UNDER AND PACKAGE CHECKING

SCALES (figs. 15 and 16)

Over and under and package checking scales are essentially balances, and are used in both industrial and commercial applications. For example, one of the uses of over and under scales is to check packages in a production process to determine if they are within prescribed fill tolerances. Similarly, package checking scales are used primarily by weights and measures enforcement officials to determine the accuracy of quantity of contents statements on packaged consumer commodities.

Metric adaptation of these devices would be desirable if packaged consumer commodities were required to be sold in metric terms (labeled with metric units). That is, since the quantity statement and the scale would be using the same measurement language, metric units, the possible errors which may be caused by the use of conversion factors in production and testing operations would be eliminated.

The adaptation of these devices essentially requires that the weighbeam and possibly the poise be replaced, and that a new chart (e.g., over and under type) be installed in the tower indicator.

Finally, most manufacturers of these devices feel that the problems of metric adaptation would be slight at both the plant and field levels. Apparently, this was due to the fact that these are relatively simple devices.

1-4. ADAPTATION OF METERING DEVICES

(MECHANICAL)

INTRODUCTION

Since the changes required to metricate present commercial mechanical metering systems are about the same, despite the fluid being dispensed, this section will confine its attention to the metric adaptation of retail gasoline pumping systems, and meters on gasoline and oil delivery trucks.

GASOLINE DISPENSING SYSTEMS (RETAIL)

Certainly, one of the most recognizable sights to the average American driver is a gasoline pump (fig. 17). What is not generally known is that these

devices in 1969 dispensed over 82 billion gallons of gasoline. The vast majority of this gasoline was purchased from 220,000+ gasoline stations in the country at an annual expenditure of about $25 billion. 10

A mechanical gasoline dispensing system is composed of three basic parts: (1) a pump, (2) a meter, and (3) a mechanical computer11 (fig. 18). The pump, usually a positive displacement type, forces the liquid (gasoline) through the meter (which contains a series of rotating adjustable calibrated chambers). As the chambers rotate they drive a shaft-gear mechanism which is connected to the computer. The computer records, for any set price per gallon, the total gallons delivered and the total sale in dollars and cents.

In order to adapt these systems to indicate in metric units, the following changes will be necessary:

a) The shaft-gear mechanism between the meter and the computer would have to be changed so that the input into the computer would be 3.785 times faster than at the present time. This is essentially a gear change only.

b) Computers that indicate to only three places in the quantity section allow readings only up to 99.9 and this indication would not be adequate if metric units are used, as such devices would be only able to indicate a

10 Statistics were obtained from National Petroleum News (NPN), Factbook Issue, mid-May 1970, (McGraw-Hill Inc., New York 10036).

11 There is only one manufacturer of this type of computer.

capacity up to 99.9 liters (26.39 gal). It is clear, that this capacity would not be adequate for filling large capacity vehicles. However, kits are available from the computer manufacturer which allow servicemen to change the left wheel indicator in the quantity section on three wheel computers to read from 0 to 14. This would allow the device to have a capacity of 149.9 liters (39.60 gal) which would be suitable for most retail operations. There would, of course, be no such problem with computers that indicate to four places since they would be adapted to record up to 999.9 liters (264.15 gal). 12 Note: (The following is new information which was received from the Gasoline Pump Manufacturers Association just prior to closing for press. Time did not permit an in depth analysis of this information to determine the possible economic impacts.)

It appears that a change in NBS Handbook 44 by the 55th National Conference on Weights and Measures may have precluded this type of adaptation for 3-wheel registers. The applicable provision is as follows:

12 The conversion kits allow present three-wheel registers to increase their capacity from 99.9 gal (376.16 liters) to 149.9 gal (567.43 liters). However, adaptation would reduce the capacity to 39.60 gal (149.9 liters), which is 26.4 percent of the present capacity. Likewise, four-wheel registers would have their capacity reduced to 26.4 percent of their capacity. This reduction in capacity could limit the usefulness of these devices.