Needle Gauge Comparison Chart

Hypodermic needles are available in a wide variety of outer diameters described by gauge numbers. Smaller gauge numbers indicate larger outer diameters. Inner diameter depends on both gauge and wall thickness. The following chart shows nominal inner diameter and wall thickness for regular-wall needles. Thin-wall needles (not shown) have identical outer diameters but larger inner diameters for a given gauge.

Needle wire gauge is derived from the Birmingham Wire Gauge. #1 = 18½ B.W.G.; #2 = 19 B.W.G., and so on to #14 = 31 B.W.G.

Needle	Nominal Outer Diameter			Nominal Inner Diameter			Nominal Wall Thickness
Gauge	inches	mm	tol. inches (mm)	inches	mm	tol. inches (mm)	inches	mm	tol. inches (mm)
7	0.180	4.572	±0.001 (±0.025)	0.150	3.810	±0.003 (±0.076)	0.015	0.381	±0.001 (±0.025)
8	0.165	4.191	"	0.135	3.429	"	"	"	"
9	0.148	3.759	"	0.118	2.997	"	"	"	"
10	0.134	3.404	"	0.106	2.692	"	0.014	0.356	"
11	0.120	3.048	"	0.094	2.388	"	0.013	0.330	"
12	0.109	2.769	"	0.085	2.159	"	0.012	0.305	"
13	0.095	2.413	"	0.071	1.803	"	"	"	"
14	0.083	2.108	"	0.063	1.600	"	0.01	0.254	"
15	0.072	1.829	±0.0005 (±0.013)	0.054	1.372	±0.0015 (±0.038)	0.009	0.229	±0.0005 (±0.013)
16	0.065	1.651	"	0.047	1.194	"	"	"	"
17	0.058	1.473	"	0.042	1.067	"	0.008	0.203	"
18	0.050	1.270	"	0.033	0.838	"	0.0085	0.216	"
19	0.042	1.067	"	0.027	0.686	"	0.0075	0.191	"
20	0.03575	0.9081	±0.00025 (±0.0064)	0.02375	0.603	±0.00075 (±0.019)	0.006	0.1524	±0.00025 (±0.0064)
21	0.03225	0.8192	"	0.02025	0.514	"	"	"	"
22	0.02825	0.7176	"	0.01625	0.413	"	"	"	"
22s	"	"	"	0.006	0.152	"	0.0111	0.2826	"
23	0.02525	0.6414	"	0.01325	0.337	"	0.006	0.1524	"
24	0.02225	0.5652	"	0.01225	0.311	"	0.005	0.1270	"
25	0.02025	0.5144	"	0.01025	0.260	"	"	"	"
26	0.01825	0.4636	"	"	"	"	0.004	0.1016	"
26s	0.01865	0.4737	"	0.005	0.127	"	0.0068	0.1734
27	0.01625	0.4128	"	0.00825	0.210	"	0.004	0.1016	"
28	0.01425	0.3620	"	0.00725	0.184	"	0.0035	0.0889	"
29	0.01325	0.3366	"	"	"	"	0.003	0.0762	"
30	0.01225	0.3112	"	0.00625	0.159	"	"	"	"
31	0.01025	0.2604	"	0.00525	0.133	"	0.0025	0.0635	"
32	0.00925	0.2350	"	0.00425	0.108	"	"	"	"
33	0.00825	0.2096	"	"	"	"	0.002	0.0508	"
34	0.00725	0.1842	"	0.00325	0.0826	"	"	"	"

What size glove do I need?

Glove Sizing Guide

1.      With hand extended flat, loosely loop measuring tape around the circumference at the knuckles (area indicated in picture)

2.      Keeping measuring tape around the knuckles, make a fist with your hand

3.      Adjust tension to match how you prefer your gloves to fit. (looser for a baggier fit, tighter for a snugger fit).

4.      Record circumference measurement in inches. Match size to chart below. The Sizing Charts below are a general approximation and can be used to assist in glove sizing. When trying on gloves, to be sure a glove fits properly it should:

a) Fit at the base of the fingers
b) Fit comfortable over the extended thumb
c) Fit comfortably at the base of the thumb
d) Not become baggy when you flex your hand

Inches	Women's Size	Men's Size
5-5.5	X-Small
5.5-6.5	Small	X-Small
6.5-7.5	Medium	Small
7.5-8.5	Large	Medium
8.5-9.5	X-Large	Large
9.5-10.5	XX-Large	X-Large
10.5-11.5		XX-Large

IP Ratings explained

IP RATING TABLE
Degree of Protection	1st Digit(Solid Objects)	2nd Digit(Liquids)
0	No Protection	No Protection
1	Protected against objects larger than 50mm	Drip Proof
2	Protected against objects larger than 12mm	Protected against direct sprays of water up to 15° from vertical
3	Protected against objects larger than 2.5mm	Protected against direct sprays of water up to 60° from vertical -light rain proof
4	Protected against objects larger than 1mm	Protected against water sprayed from all directions-light splash proof
5	Protected against dust limited ingress	Protected against low pressure jets of water from all directions -limited ingress permitted
6	Totally protected against dust	Protected against low pressure jets of water (use on ship deck) -limited ingress permitted
7	Not Defined	Protected against the effect of immersion between 150mm & 1 metre
8	Not Defined	Protected against long periods of immersion under pressure

pH Measurement theory and Electrodes

pH Measurement

The measurement of pH using a pH Electrode is an age old method that centres around
the perception of a substance as acidic or alkaline and is dependent on the concentration
of the hydrogen Ion (H+) within the substance.

The use of a pH electrode allows this measurement to be expressed in a meaningful way.

Derived from the Sorensen Equation the pH value is defined as a negative logarithm of the H+ concentration in a given solution.

A high H+ Concentration equals: 1mol/L = 10o pH = 0 (ACIDIC)

A low H+ Concentration equals: 10-14 mol/L pH=14 (ALKALINE)

It is therefore simple to measure the pH of a substance and compare it with other substances. pH 0 is extremely acidic, pH 14 is extremely alkaline and pH 7 neutral.

Measuring pH Values

Measuring the pH of a substance requires the use of a pH Electrode and a Reference Electrode. The pH Glass at the end of the electrode acts as the sensing part of the circuit.

The second part of the circuit is the reference electrode. This is a stable point that has a defined potential and is independent of the solution to be measured. The reference electrode fig is made up of a reference element that is commonly a Silver/Silver Chloride wire encased in a known electrolyte. The reference electrode then has a junction, which is the contact between the stable internal reference electrode and the solution to be measured. This is commonly a porous ceramic pin.

The evolution of pH electrodes came with the joining of the two separate electrodes to produce the COMBINATION pH ELECTRODE. The formation of the combination electrode can be seen below. The formation of the combination electrode still has the pH Glass membrane acting in the same way. The reference electrode is continually encased around the pH electrode. As the pH Glass comes into contact with an aqueous substance to measure, a gel layer forms on the membrane. This also happens on the inside of the glass layer. The pH value of the aqueous solution will either force Hydrogen Ions out of the Gel layer or into this layer. The Internal buffer in the glass electrode has a constant pH value and this keeps the potential at the inner surface of the membrane constant. The membrane potential is therefore the difference between the inner and outer charge. If you then factor in the reference electrode with its stable potential you have a combination pH electrode that encapsulates the measuring electrode and reference electrode.

P&R Labpak are able to offer a huge range of electrodes and through it’s electrode supplier Sentek can offer their equivalents which are less expensive and yet are the same or better quality.  Contact us on 0870 034 2055 or e-mail us at sales@prlabs.co.uk with your electrode enquiries.

 

How the pH Electrode Works

As the pH Glass comes into contact with an aqueous substance to measure, a gel layer forms on the membrane.
This also happens on the inside of the glass layer.

The pH value of the aqueous solution will either force Hydrogen Ions out of the Gel layer or into this layer.
The Internal buffer in the glass electrode has a constant pH value and this keeps the potential at the inner
surface of the membrane constant.

The membrane potential is therefore the difference between the inner and outer charge.
If you then factor in the reference electrode with its stable potential you have a combination
pH electrode that encapsulates the measuring electrode and reference electrode.

Visit www.prlabs.co.uk for more information or to contact us.  Check out our news pages for special offers – www.prlabs.co.uk/news

Whatman filter papers - Which one to use?

The download link below is a pdf document detailing which Whatman filter papers to use for which application.  Just click on the link below.

PDF download

If you require any help with filtration just contact our sales desk - sales@prlabs.co.uk or call us on 0870 034 2055.