Omega Engineering PHTX-11 manual Controls

PART III - OPERATING INSTRUCTIONS & TECHNICAL INFORMATION

1.Controls

1.1 Display switch is 1abeled"Press for mA" on the cover. The display will indicate 0.00 pH to 14.00 pH when the switch is in the relaxed position.

When the switch is pressed and held, the display will indicate the output current to mA, normally 4.0 mA to 20.0 mA.

1.2 "pH CAL" potentiometer is an offset adjustment for the		pH probe on the
input circuit board.	This adjustment allows standardization of different
probes, it affects the displayed readout and the output current.

1.3"Slope" potentiometer is a gain adjustment on the input circuit board. This adjustment is used to standardize the readings for probes with less

than 100% efficiency, it affects the displayed readout and the output current.

1.4"R19" potentiometer is a gain adjustment on the output circuit board. This adjustment is factory set and should not need adjustment in the

field, it affects the displayed pH readout only.

1.5	"ZERO" potentiometer is an offset adjustment on the output board.								This
	adjustment sets the 4			mA output current level for the desired			pH	level,
	it is used in conjunction with the range switch.					The “Zero" pot affects
	the output current only.			There is interaction between the "Zero" and
	"Span" pots.
1.6	"SPAN" potentiometer is a gain adjustment on the output board.							This
	adjustment sets the 20			mA output current level for the desired			pH		level,
	it is used in conjunction with the range switch.					The "Span" pot affects
	the output current level only.				There is interaction between the "Zero"
	and "Span" pots.
1.7 Range jumpers are located on the output board.						These jumpers allow the
	user to increase the sensitivity of the output.					There are 4 jumper pairs
	of pads, the uppermost position is not used; there are no traces connected
	to this pair of pads.			Jumper	#l is located in the pair of		pads	second
	from the	top,	and this jumper is for full scale output currents of 6
	to 14 pH units.		Jumper #2 is located in the third pair of pads, it may
	be added	to obtain a full scale output of 2 to 6				pH units.	Jumper		#3
	is added	for a full scale output of 1 to 2				pH units.

2.Operation

2.1Initialization of the transmitter consists of making the connections

described in the wiring (section II-31 of this manual and placing the

sensor	in a known buffer solution and turning the power on.		The display
should	indicate the	pH value of the buffer solution.

2.2Probe standardization is accomplished by adjusting "pH CAL" with the probe in a 7.0 pH buffer solution for a reading of 7.0 and the "Slope" adjustment.when the probe is in a 4.0 pH or a iO.0 buffer solution.

The choice of a 4.0 or 10.0 is up to the user.

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