Classic Computer Magazine Archive CREATIVE COMPUTING VOL. 11, NO. 2 / FEBRUARY 1985 / PAGE 80

Amplot II; the Amplot II is an easy to use capable six-pen flat-bed plotter at a modest price. (evaluation) David H. Ahl.

The Amplot II is a six-pen, flat-bed plotter that is quite easy to use. It has 20 drawing commands, reasonably high resolution, and built-in parallel and serial (RS-232) interfaces--all at a very modest price. It even comes with a protective plastic cover.

Interfacing the plotter, particularly through the parallel port is extremely simple (although you would never know it from reading the manual). The Amplot II has a Centronics-type connector on the rear; a printer cable from the computer works just fine. The serial interface is only slightly more complicated; it requires a null modem cable (pin 3 to 4, etc.) and can be set to any of five baud rates (300 to 4800), 7 or 8 data bits, and parity, and 1 or 2 stop bits. The important thing is to make sure your computer matches the settings on the plotter.

The Amplot II can handle up to international paper size A3 (11.7" x 16.5") as well as U.S. standard 11" x 17". The effective drawing area is 270 x 400 mm (10.6" x 15.7"). Paper is held down by a paper guide at the bottom of the plotter bed and two 7" magnetic strips at the top.

Six fiber tip pens are furnished with the plotter, one each of red, orange, green, blue, violet, and black. Aqueous fiber tip and oily fiber tip pens (for drawing on acetate) are also available. The pens are loaded by simply dropping them into the six holders at the left of the plotter bed.

Commands are sent to the plotter from Basic, either in an LPRINT statement (parallel interface) or PRINT #1 (serial interface). Commands must be sent as capital letters enclosed in quotation marks, while numeric amounts may be sent as number (120, 175) or variables (x, y) not enclosed in quotes.

The plotter surface is divided into 0.1 mm lengths (2700 x 4000), and plotter coordinates are specified in millimeters. The origin may be set any place with the drawing area; for example, if it is in the center, plotting coordinates can range between [plus-or-minus] 1350 and [plus-or-minus] 2000. There are no scaling capabilities.

Commands include the expected Draw Absolute, Draw Relative (with respect to the last point), Move Absolute, and Move Relative. Line Type specifies solid and three types of dashed lines, while Line Scale sets the repetitive length of line segments; combining both commands allows drawing ten or more distinctive types of lines. Axis draws an x or y axis with hash marks at specified intervals.

The Circle command draws a circle or arc of any radius. Unlike the more general command found on some plotters, this one cannot draw ellipses.

The Home command moves the pen to the lower left position, while Z moves it to the top center. ASCII characters can be printed in any of the four compass directions. "Standard" character sizes range from 3 mm to 11.2 mm high, although it is possible to specify the height and width of a character (up to 200 x 200 mm). Six graphing marks can be drawn in sizes up to 10 mm.

Pen speed can be set to either normal (200 mm/sec) or slow (100 mm/sec). We found the normal speed was satisfactory for all of our tests. The paper Size. command limits the effective drawing area for paper sizes smaller than A3, while the Window command also limits the effective drawing area, temporarily, for drawing several charts on one piece of paper. Making Plots

We found it quite easy to take programs written for other plotters and adapt them to the Amplot II. In general, only a few minor changes were necessary in plotter commands and variable values. During conversion, this led to some errors when values were out of range or when incorrect commands were sent to the plotter. When the plotter receives an erroneous command or value, it halts and a red LED comes on. The error can be cancelled by pressing any one of the four pen direction switches; this clears the data buffer and readies the plotter to accept more commands. (Actually, when debugging a plotter program, we find it best to do so without a pen in the holder. When things "look" right, it can be run with a pen.)

As mentioned earlier, the step size is 0.1 mm; the manufacturer-specified repetition accuracy is 0.3 mm with the same pen or 0.4 mm with different pens. In practice, we found the accuracy to be better than that.

The manual contains two sample programs for drawing a bar chart and a combined bar and pie chart. We weren't enthralled with the efficiency of coding, but the programs are well-explained and demonstrate most of the plotter features. Notes at the end of the manual offer helpful tips on how to use the plotter with a IBM PC and overcome the Device Timeout problem. Users for other computers will find these tips helpful as well.

All in all, we were impressed with the Amplot II. It is easy to use, has both serial and parallel interfaces, and has good resolution and accuracy. While it is not in the same league as the Houston instruments DMP-29 (which costs more than twice as much), it is an able competitor in the $1000 multi-pen plotter derby.

Products: Amplot II (computer printer)