Electronic weighing scales
see:
Weighing Scales for Kenya
Electronic weighing scales Andrew Hall 29.10.99
Fw: Electronic weighing scales Ibrahim Parvanta 29.10.99
Re: Electronic weighing scales Lois Englberger 30.10.8
Re[2]: Electronic weighing scales Olivia Yambi 31.10.8
Measuring Equipment David Morley 01.11.99
Evaluation of scales used in field research Ken Porter 01.11.99
infants and measuring weight change Michael Golden 01.11.99
Electronic weighing scales - results soehnle scale Brad Woodruff 11.11.99


From: Andrew Hall <andrew.hallatwellcome-epidemiology.oxford.ac.uk>

Subject: Electronic weighing scales

Date: Sun, 24 Oct 1999 11:04:51 +0100

 

Could I have benefit of people's experience of electronic scales that weigh to an precision of <=0.2 kg and are robust enough to be carried around in the field? I am often asked to recommend scales but no particular model stands out in my experience as reliable, accurate, robust and inexpensive, so I'd like to know what professional nutritionists think.

I'd like to know: make and model; number of scales in use; how long the scale or scales have been used without trouble; and what problems, if any have been experienced? For example: do you have any problems with the solar switch on the UNICEF model? Positive feedback as well as negative feedback would be appreciated. If I get a reasonable sample size of replies (both people and scales) I'd be happy to try and summarise the reports and post it to NGO Nutrition.

I am particularly interested in the following scales as they have a sealed unit design and can withstand being moved about, unlike most bathroom-type scales.

  1. UNICEF scale, accuracy 0.1 kg. Model with a solar switch next to the digital readout and an internal irreplaceable battery supposedly good for 1 million weighings. (Also sold by SECA as models 870 or 871, now discontinued?).
  2. The new replacement for the above? Model with 4 AA batteries and turns on by touching the top. (Sold by SECA as model 873).
  3. Tanita THD-305 with the same sealed design as 1 and 2, has a separate on/off switch and takes 4 AA batteries.

Thanks for your time and for any advice and experience that you can give.

Andrew Hall

 

Dr. Andrew Hall, Programmes Coordinator, Partnership for Child Development.

Wellcome Trust Centre for the Epidemiology of Infectious Disease, Oxford University, South Parks Road, Oxford OX1 3FY, UK.

Tel: + 44 - (0)1865 - 281231, Fax: + 44 - (0)1865 - 281245

WTCEID http://www.ceid.ox.ac.uk/

PCD: http://www.ceid.ox.ac.uk/child


From: "Parvanta, Ibrahim" <ixp1atcdc.gov>

Subject: FW: Electronic weighing scales

Date: Fri, 29 Oct 1999 09:47:15 -0400

 

Dear Dr. Hall,

The Centers for Disease Control and Prevention, and the Emory University School of Public Health in Atlanta, are planning an evaluation of anthropometric equipment, including scales. We hope to have a report of our study by early next year. Among other devices, we plan to evaluate the Uniscale (from UNICEF) and the Tanita #1582. We will see if we can add the Tanita THD-305 to the list. I am sharing this message with Dr. Rachel Albalak at Emory University. If you have any other questions or comments, please contact her at <ralbalaatsph.emory.edu>.

Best regards,

 

Ibrahim (Abe) Parvanta, Chief, International Activities

Maternal and Child Nutrition Branch, Division of Nutrition and Physical Activity CDC Atlanta, GA

tel: 770-488-5865, e-mail: ixp1atcdc.gov


Date: Sat, 30 Oct 1999 19:24:34 +0100

From: "Nutrition" <nutritionatmail.fm>

Subject: Re: Electronic weighing scales

 

I would like to respond to Dr. Hall's question on electronic scales. A few years ago, I was working in the Kingdom of Tonga, where I was involved in organizing the Tonga Healthy Weight Loss Competition. The purpose of that activity was to increase awareness of the health risks to overweight and obesity. The activity was quite successful in fact, and attracted attention from the international media. It has now become an annual event, just completing this year its 5th annual competition.

The King of Tonga is famous for his support of the competition, and in his own personal success at weight loss and weight loss maintenance. He lost a total of 70 kg, going from 200 kg in 1976 to 130 kg in 1996, maintaining his weight loss with both diet and exercise. He encourages his people to follow his example.

We used a few different electronic scales, there was no problem in this for the competition as the participants were required to weigh only at one weigh station. However, we did have problems with some scales breaking, unreliable measurements, transporting scales to the different weigh stations which needed to share, due to the insufficient number of scales for all stations to have their own.

Our best experience was with the UNICEF Seca Electronic Scale 890. It was a solar scale, and there was no problem in the daytime, but was not reliable at night. We had 5 of these scales, two did in fact break, but there were problems in handling the scales in both cases, once the scales being dropped with great force, and in the other case, poor care taken in stepping on the scales with the heavy participants standing on the scales in reverse, that is standing on the glass solar cell panel area. These were the reports from the managers of the weigh stations. We had many participants with weights over 100 kg, with up to a thousand participants weighing monthly for the six-month period, which speaks well for the scales. The maximum of those scales was 150 kg. The precision was good, to 0.1 kg. The cost of these scales as purchased through UNICEF was not high.

We had 11 Soehnle Electronic scales, also with a maximum of 150 kg. These scales were not very reliable, we had problems with them from the beginning. These scales required batteries, this was also a problem.

We had two Tanita body fat monitoring scales, which were small transportable scales similar in appearance to the other scales, but which gave % body fat measurements. These scales were quite sturdy, though there was a problem in taking the % body fat of some Tongans. It was later suggested by the company, on our communications with them on the problem, that there seem to often be problems with taking body fat measurements from people who often go barefoot as the skin becomes too tough for good contact. These scales provide the body fat measurements by using bioelectric impedance.

I can get the model number for the Soehnle and Tanita scales, if you need.

Greetings,

Lois Englberger

 

Lois Englberger, UNICEF Health and Nutrition Advisor

P. O. Box 2299, Kolonia, Pohnpei 96941

Federated States of Micronesia


Date: Sun, 31 Oct 1999 13:19:29 -0800

From: oyambiatunicef.org (Olivia Yambi)

Subject: Re[2]: Electronic weighing scales

 

UNICEF NYHQ has conducted a compiled information from a number of country experiences on the use of the SECA scale. By copy of this email, I am requesting my colleagues in Nutrition Section, NYHQ to circulate the report.

 

Olivia Yambi

INICEF - ESARO


Date: Mon, 01 Nov 1999 12:33:32 +0000

From: David Morley <Davidatmorleydc.demon.co.uk>

Subject: Measuring Equipment

 

Dear Dr Ibrahim Parvanta,

Teaching Aids at Low Cost (TALC) is developing a series of measuring equipment which are aimed to be used by the community or family. Our objective is both to improve health and increase understanding of numeracy in the style that Paulo Friere developed for literacy. I very much hope that the Emory University and the CDC analysis of measuring equipment will examine these along with others.

The Direct Recording Scale (DRS) has a number of advantages:

  1. Unschooled Maasai Mothers themselves plot the weight curve of their children and along with the grandmothers,and daughters understand the significance of faltering and in the Maasai give extra feeds to their children when this occurs.
  2. The DRS is almost indestructible,I throw it on concrete floors and jump on it, no one forgets that demonstration!
  3. It costs about half the cost of a standard "Salter" dial scale.

Its disadvantage is that it can be only used with charts in which the Kg.

line are exactly 1cm apart,and the zero line 3.5 cm from the bottom edge of the charts. Thirty charts are supplied with each scale, they are available in 8 languages. As far as I know only national charts in the Republic of South Africa meet these criteria. This is necessary as the large spring made to a specification of 1% accuracy (ie 100gms) stretches 1cm / Kg up the chart, the mother puts the next 'dot' through a large hole in a pointer at the top of a spring.[ If you look though UNICEF record you will find that they tried out some DRS which were inaccurate, this was because I was persuaded to use stainless steel springs, not realising these are totally inaccurate]

 

TALC also has low cost arm circumference tapes, a metre long circumference tape and is developing a Symphisis Putbis - Fundal tape, and a low cost accurate height measure (this does need some skill in its erection) both available we hope early next year.

I will be sending you the published work on the scale, a sample scale and circumference tapes, together with an unpublished article describing this approach. If anyone else in 'Ngonut' is interested in trying them out do contact me or TALC. David Morley.

 

David Morley,Emeritus Professor of Tropical Child Health, University of London.

Davidatmorleydc.demon.co.uk

Tel: & Fax. 44 (0) 1582 712199.

Preferred Address; 51 Eastmoor Park, Harpenden, AL5 1BN. UK.


Date: Mon, 01 Nov 1999 17:57:37 +0000

From: Ken Porter <ken.porteratlinacre.oxford.ac.uk>

Subject: Evaluation of scales used in field research Sender: owner-ngonutatabdn.ac.uk

 

Colleagues:

On the matter of scales raised by Andrew Hall... In my research on the adolescent growth of Burundians living in refugee camps in northwest Tanzania I used a solar-powered digital display SECA Omega 870 bought new from CMS Weighing (London) in August, 1998. CMS had certified the accuracy at purchase saying that it would be accurate to 0.1 kg over a range from 1 - 150 kg. In the field I regularly checked the calibration by use of a standardised water weight that I made up using a different small electronic scale that was accurate to 1gm. The SECA scale remained accurate throughout 3 months of continuous use.

On my first day and in my first hour of field use an error message flashed on the display and no readings were possible. (I had to frantically borrow a balance arm scale from the dispensary to continue measurements.) It turned out that the error was caused by strong direct light. The moment that the scale was set up in shade it worked without problem. In outdoor locations it meant that we had to move the scale as the shadows moved. It continued to work in relatively deep shade, but would stop functioning in dark corners inside buildings. If an error message was evoked it could take up to 10 minutes before the scale would allow itself to be reset.

We found that if the surface was not flat and reasonably stable we could not get a reading - it just continued to flash '1' alternately on the left and right. Bare ground just could not be used because despite efforts to find level ground the scale eventually became wobbly as repeated use broke up the earth under the scale. The problem of stability was easily solved - we put a couple of wooden clip-boards underneath directly on reasonably flat bare ground.

Where the subject stood on the platform did not seem to affect the reading - middle, front, sides or back... the readings remained the same. If the subject fidgetted, however, it took a good while for the reading to be displayed. This was a good feature, I think. If the child stood still the measurement would display in about seven seconds. The display is large and easily read.

The machine was surprisingly rugged. We observed no distortions in the platform or in the housing either temporarily during the trials or permanently at any time afterwards. The unit was carried to and from the field daily being bounced around in the back of a Land Cruiser over dreadful Tanzanian roads. It was used for more than 4200 weighings as part of the study and doubtless at least that many more in trials and for the amusement of staff and village elders. It seemed impervious to dust and mud and was easily cleaned up.

All in all, I was wholly satisfied with its performance.

Cheers

 

Ken Porter, Doctoral Candidate

Institute of Biological Anthropology, University of Oxford

Off: Institute of Biological Anthropology, 58 Banbury Road, Oxford, UK OX2 6QS

Res: Linacre College, St Cross Road, Oxford, U.K. OX1 3JA

Tel: New number 44 + (0)1865 + 281 470] Fax: 44 + (0)1865 + 274 699


Date: Mon, 01 Nov 1999 18:59:28 +0000

From: Michael Golden <m.goldenatabdn.ac.uk>

Subject: infants and measuring weight change

 

Dear NGONUTS,

The scales that are used for surveys are often also used in a Hospital, TFC or SFC for assessing and monitoring children's progress. "Survey" scales are not useful for that purpose - certainly not for young infants; it is necessary to have scales with a higher degree of precision. Most beam balance "baby weighing scales" in the field are hopeless and nearly all that I've seen are dusty from long disuse.

If a child of 5 kg is gaining weight at 5 g/kg/d he will gain a total of 25g per day - it will really take 8 days to tell whether the child is gaining weight (2 divisions on a 0.1kg scale). To differentiate "failing" from "not-failing" , that is between a rate of weight gain of less than or more than 5g/kg/d is impossible within the time frame of treatment of a severely malnourished child. For an supplementary feeding program the same considerations apply as the rates of weight gain that have to be differentiated are between 0 and 2g/kg/d. The situation is much worse for a 3kg child and not even adequate for a 10 kg child.

Scales with a precision of only 0.1kg or less should not be purchased for use in monitoring nutrition rehabilitation.

An accurate scale has other very important clinical uses. For example if a child gets diarrhoea after admission the amount of fluid lost can be quickly and accurately assessed by taking the child's weight - indeed, by far the best, most accurate and easiest way to manage a child with diarrhoea is to take accurate weights - this immediately gives a measure of fluid balance. Similarly, if there is heart failure from excess fluid administration and retention - a scale will tell you how much has been retained since the last weighing. It should be standard clinical practice to weigh children during treatment of "dehydration" or transfusion etc.

Again such clinical uses in small children require a scale that is much more precise than 0.1kg or worse (150g is 5% of a 3kg child's weight!).

Diets, cups and feeds can also be usefully measured on a more accurate scale and breast-milk intake assessed with before-and-after weighting..

There is a need for a good, robust clinical scale that reads to 0.01kg and can weight infants, children and adults using the same instrument. Such a scale would also be useful for surveys - but not the reverse.

Inadequate scales on the field (and parsimony about the cost of this vital piece of equipment) are one of a main impediment to the successful management of malnourished individuals or other situations where repeated measurements are crucial.

 

Mike Golden


Date: Thu, 11 Nov 1999 11:43:48 +0000

From: "Woodruff, Brad" <baw4atcdc.gov>

Subject: Electronic weighing scales - results soehnle scale.

 

Dear NGONut readers:

We have some experience with one model of Soehnle scale. Not sure what the model number is, but the box says "Galaxy 7504.00.900." These scales require a disk-shaped lithium battery type CR2430 which is very hard to find in the field. When purchased in March 1996 and checked with a standard weight (the same individual), all 10 scales gave readings within 0.1 kg.

All scales were used for one month in a household nutrition survey, during which they were carried to selected households and generally abused. Some of the scales were then used occasionally thereafter, but not in rough conditions. In preparation for another survey, eight of the scales were rechecked in October 1998. I weighed myself using a medical balance scale and a UNICEF scale. I then stepped on each of the eight Soehnle scales three times. Below are the results. Of note, one of the scales, number 4, gave three readings which differed by 0.6 kgs. All gave lower readings those obtained by the balance scale and the UNICEF scale. In addition, the plastic housing of many of the scales has broken with use.

In summary, we have not found this model of Soehnle scale very robust or accurate and would not use them again in a field nutrition survey.

Regards,

Brad Woodruff

International Emergency and Refugee Health Branch, Centers for Disease Control and Prevention (CDC) Atlanta, Georgia USA